Effectiveness of MF59-adjuvanted subunit influenza vaccine in preventing hospitalisations for cardiovascular disease, cerebrovascular disease and pneumonia in the elderly. Guillain-Barre syndrome following vaccination in the National Influenza Immunization Program, United States, 1976--1977. Different protection rates in various groups of volunteers given subunit influenza virus vaccine in 1976. Impact of influenza A in a nursing home. Study of the effectiveness of influenza vaccination in the elderly in the epidemic of 1989-90 using a general practice database. Effectiveness of influenza vaccination in preventing influenza-like illness among community-dwelling elderly: population-based cohort study in Japan. Two outbreaks of influenza A (H3N2) in a Japanese nursing home in the winter of 1996-1997, with differing vaccine efficacy. [Effectiveness of an anti-influenza vaccination program in 4 primary care centers]. The effectiveness of influenza vaccine against influenza a (H3N2) virus infections in nursing homes in Niigata, Japan, during the 1998-1999 and 1999-2000 seasons. Influenza A/Philippines/2/82 outbreak in a nursing home: limitations of influenza vaccination in the aged. Influenza outbreaks in nursing homes: how effective is influenza vaccine in the institutionalized elderly? The roles of vaccination and amantadine prophylaxis in controlling an outbreak of influenza A (H3N2) in a nursing home. [Efficacy of influenza vaccination: results in a community controlled for 2 years]. Influenza vaccination in community-dwelling elderly: impact on mortality and influenza-associated morbidity. A prospective, Internet-based study of the effectiveness and safety of influenza vaccination in the 2001-2002 influenza season. Influenza vaccine effectiveness in preventing hospitalization for pneumonia in the elderly. Additive preventive effect of influenza and pneumococcal vaccines in elderly persons. Guillain-Barré syndrome in the United States, 1979-1980 and 1980-1981. Lack of an association with influenza vaccination. Failure of inactivated influenza vaccine to protect an aged population. A case-control study of elderly patients with acute respiratory illness: effect of influenza vaccination on admission to hospital in winter 2003-2004. Influenza vaccine effectiveness in preventing hospitalization among the elderly during influenza type A and type B seasons. Influenza vaccination programs for elderly persons: cost-effectiveness in a health maintenance organization. Is influenza vaccination cost effective for healthy people between ages 65 and 74 years? A randomised controlled trial. An outbreak of influenza A (H3N2) in a well immunized nursing home population. Effectiveness of inactivated influenza vaccine among nursing home residents during an influenza type A (H3N2) epidemic. A cohort study of the effectiveness of influenza vaccine in older people, performed using the United Kingdom general practice research database. Efficacy of influenza vaccine in nursing homes. Reduction in illness and complications during an influenza A (H3N2) epidemic. Benefits of influenza vaccination for low-, intermediate-, and high-risk senior citizens. Immunogenicity and efficacy of Russian live attenuated and US inactivated influenza vaccines used alone and in combination in nursing home residents. Influenza in a partially immunized aged population. Effectiveness of killed Hong Kong vaccine against infection with the England strain. Age-related responses to influenza vaccination in the Newcastle region during 1983 and 1984. Influenza in the elderly: report of an outbreak and a review of vaccine effectiveness reports. Reduction in hospital admissions for pneumonia in non-institutionalised elderly people as a result of influenza vaccination: a case-control study in Spain. Influenza A among community-dwelling elderly persons in Leicestershire during winter 1993-4; cigarette smoking as a risk factor and the efficacy of influenza vaccination. Influenza vaccine and pneumonia mortality in a nursing home population. Effectiveness of influenza vaccine in reducing hospital admissions during the 1989-90 epidemic. Reduction in mortality associated with influenza vaccine during 1989-90 epidemic. Increasing doses of purified influenza virus hemagglutinin and subvirion vaccines enhance antibody responses in the elderly. Evaluation of monovalent influenza vaccine in a retirement community during the epidemic of 1965-66. Evaluation of cold-adapted, reassortant influenza B virus vaccines in elderly and chronically ill adults. Adverse reactions to influenza vaccine in elderly people: randomised double blind placebo controlled trial. The efficacy of influenza vaccination in elderly individuals. A randomized double-blind placebo-controlled trial. Efficacy of the antiinfluenza A vaccination during epidemics due to A/VIC/3/75 and A/Texas/1/77 viruses. [Analysis of an influenza vaccination campaign in rural environment]. Influenza vaccination, hospitalizations, and costs among members of a Medicare managed care plan. Outbreak of influenza A in an Ontario nursing home--January 1997. Frequency of adverse reactions to influenza vaccine in the elderly. A randomized, placebo-controlled trial. Influence of high-risk medical conditions on the effectiveness of influenza vaccination among elderly members of 3 large managed-care organizations. Influenza vaccination: reduction in hospitalizations and death rates among members of "Maccabi Healthcare Services" during the 2000-2001 influenza season. Association of influenza immunization with reduction in mortality in an elderly population. A prospective study. Influenza vaccine effectiveness in preventing hospitalizations and deaths in persons 65 years or older in Minnesota, New York, and Oregon: data from 3 health plans. The Guillain-Barré syndrome and the 1992-1993 and 1993-1994 influenza vaccines. Effects of a large-scale intervention with influenza and 23-valent pneumococcal vaccines in adults aged 65 years or older: a prospective study. Lessons from a nursing home outbreak of influenza A. Unusual outbreak of influenza A in a Wyoming nursing home. Clinical effectiveness of influenza vaccination in Manitoba. Spread of influenza: a study of risk factors in homes for the elderly in Wales. Influenza vaccine efficacy in a Maryland nursing home. Nursing home outbreak of influenza A (H3N2): evaluation of vaccine efficacy and influenza case definitions. Influenza vaccine effectiveness among elderly nursing home residents: a cohort study. The efficacy and cost effectiveness of vaccination against influenza among elderly persons living in the community. Effectiveness of the MF59-adjuvanted influenza vaccine in preventing emergency admissions for pneumonia in the elderly over 64 years of age. [Effectiveness of anti-flu vaccine in the elderly]. Effectiveness of influenza vaccination in the elderly in a community in Italy. Efficacy of Influenza Vaccine in Elderly Persons in Welfare Nursing Homes: Reduction in Risks of Mortality and Morbidity During an Influenza A (H3N2) Epidemic. A comparison of subcutaneous, nasal, and combined influenza vaccination. II. Protection against natural challenge. Influenza vaccination and reduction in hospitalizations for cardiac disease and stroke among the elderly. An outbreak of influenza A in a nursing home. Influenza vaccination and mortality from bronchopneumonia in the elderly.
Annual circulation of influenza virus coincides with a peak in cardiovascular and pneumonia mortality/morbidity. This study aimed to determine the effectiveness of MF59-adjuvanted subunit influenza vaccine in preventing hospitalisation due to acute coronary syndrome (ACS), cerebrovascular accident (CVA) and pneumonia in the elderly. Three case-control studies were performed during the 2004-2005 influenza season in three health districts in Valencia, Spain (total elderly [>64 years of age] population: n=105,454). Controls were patients admitted for an acute surgical process or trauma within 10 days of case admission. In total, 159 patients were hospitalised for ACS, 148 for CVA and 242 for pneumonia. The risk of hospitalisation after the start of the influenza season was significantly lower in vaccinated patients compared with non-vaccinated patients (adjusted odds ratios: 0.13 [P=0.013] for ACS; 0.07 [P=0.007] for CVA; 0.31 [P=0.005] for pneumonia). During peak virus circulation, vaccination with MF59-adjuvanted subunit influenza vaccine was associated with an 87% relative risk reduction in hospitalisation for ACS, 93% for CVA, and 69% for pneumonia. Because of an increase in the number of reports of Guillian-Barre syndrome (GBS) following A/New Jersey influenza vaccination, the National Influenza Immunization Program was suspended December 16, 1976 and nationwide surveillance for GBS was begun. This surveillance uncovered a total of 1098 patients with onset of GBS from October 1, 1976, to January 31, 1977, from all 50 states, District of Columbia, and Puerto Rico. A total of 532 patients had recently received an A/New Jersey influenza vaccination prior to their onset of GBS (vaccinated cases), and 15 patients received a vaccination after their onset of GBS. Five hundred forty-three patients had not been recently vaccinated with A/New Jersey influenza vaccine and the vaccination status for 8 was unknown. Epidemiologic evidence indicated that many cases of GBS were related to vaccination. When compared to the unvaccinated population, the vaccinated population had a significantly elevated attack rate in every adult age group. The estimated attributable risk of vaccine-related GBS in the adult population was just under one case per 100,000 vaccinations. The period of increased risk was concentrated primarily within the 5-week period after vaccination, although it lasted for approximately 9 or 10 weeks. Different rates of protection were observed in various groups of volunteers given trivalent subunit influenza virus vaccine during an epidemic caused by A/Victoria/3/75 strains of influenza virus in Melbourne, Victoria, Australia, in 1976. The degree of protection varied from 80% protection from infection in one group to a moderation in the severity of clinical illness in a geriatric group. The response to immunization may depend on the previous experience of the vaccinees, and it may be necessary to use different dose schedules in different groups for optimal protection. Outbreaks of influenza A in the institutionalized elderly have been reported only rarely. Such an outbreak occurred in a nursing home in the period Dec 12, 1980, through Jan 21, 1981. Thirty (25%) of the 120 residents had onset of influenza-like illness during the outbreak. Influenza A/Bangkok/79-like (H3N2) virus was isolated from throat swab specimens from five of eight acutely ill patients. Thirteen persons were hospitalized; nine persons died (case-fatality ratio, 30%). This outbreak documents that mortality associated with an influenza outbreak can be substantial in a closed population of the elderly. Because nursing home residents are an easily accessible high-risk population, control and prevention of influenza should be a high priority in nursing homes. The effectiveness of influenza vaccination in preventing serious illness and death was determined in an elderly population during the influenza epidemic of was determined in an elderly population during the influenza epidemic of was determined in an elderly population during the influenza epidemic of 1989-90. A retrospective cohort study was carried out using computerized general practitioner records on nearly 10,000 patients aged 55 years and over. After adjustment for potential confounding factors, recent immunization was found to have a protective effect of 75% (95% confidence intervals: 21-92%) against death. Protection did not appear to vary with either age or the presence of underlying chronic disease. As the complications of influenza are most common in those with underlying chronic disease, the study findings are consistent with the recommended policy for the use of influenza vaccine in the UK. Further work is necessary to determine the cost-effectiveness of extending immunization to other groups. A population-based cohort study was conducted during the 2003-2004 season to examine the effectiveness of influenza vaccine among community-dwelling elderly. The subjects consisted of 4787 elderly, ranging from 65 to 79 years. We either interviewed the elderly directly or their families regarding acute febrile illness, hospital visits, hospitalization and death by telephone every month. The vaccination status and physician-diagnosed clinical influenza (hereinafter referred as clinical influenza) were determined based on data obtained from the city office and hospitals, respectively. Influenza-like illness (ILI) was defined as an acute febrile illness (> or = 38.5 degrees C) during the epidemic period. After adjusting for confounders, vaccination decreased ILI significantly (odds ratio [OR], 0.38; 95% confidence interval [CI], 0.17-0.85), but not clinical influenza (OR, 0.76; 95% CI, 0.28-2.06). The results were inconclusive for preventing hospitalization for influenza or pneumonia (OR, 0.37; 95% CI, 0.09-1.47) and death (OR, 3.68; 95% CI, 0.75-18.12), due to the inadequate sample size. In conclusion, the influenza vaccination was thus found to be associated with a decreased ILI during the epidemic period in community-dwelling elderly. Sixty of 128 (46.9%) residents of a nursing home were immunized with two doses of the trivalent split influenza vaccine. They developed 7.4-11.5-fold antibody increases, with a 69-82% protection rate, presenting good immune response rates to the influenza vaccine. Two outbreaks of influenza A (H3N2) occurred. There were no significant antigenic differences among the vaccine strain and the strains isolated from both outbreaks in haemagglutination-inhibition tests, suggesting that the second might have been a reoccurrence. There were no residents who were infected in both outbreaks. The vaccine efficacy against clinical illness in the first outbreak of typical influenza-like-illness (ILI) was 51% (relative risk: 0.49), and the febrile period was reduced significantly by vaccination. In the second outbreak, however, in which all patients had atypical ILI with a high fever but not respiratory symptoms, vaccine efficacy was not apparent for unknown reason. A influenza immunization programme held in 4 health centres is evaluated, by testing the hypothesis that programme compliance lowers their hospital admissions and mortality. A cohort of 4,558 people over 65 belonging to 4 "Baix Llobregat" health centres was followed-up during 7 months. The population covered by immunization programme (43.8%) showed a hospital admission rate (6.2%) lower than the non immunized one (4.3%). Nevertheless, the cardiorespiratory disease admission rate in the whole sample (2.0% in immunized and 1.3% in non immunized), and in females (1.3% in immunized and 1.2 in non immunized) didn't show differences between covered and non covered by the programme. Mortality is lower in compliant (0.8% in immunized, and 1.9% in non immunized), but it's due to a higher death rate in the counted unimmunized, non demanding, and non hospital admitted population. If we interpret these data as the immunization covered population is more health services consumer, we can consider that at least in women, the programme has a contention effect for cardiorespiratory disease hospital admission. The mortality drop can not be attributed to immunization but it will be due to the health centers incapacity for reaching the high risk population of the assigned community. On the basis of these results, health centers should reconsider the need for continuing carry out these immunizations programmes. Primary Health care teams should establish programmes that would allow them to cover the assigned community health needs, even for non demanded services. To evaluate the effectiveness of influenza vaccines against influenza-like illness (ILI) among nursing home residents.
                Prospective, nonrandomized, cohort study.
                Nine nursing homes during the 1998-1999 influenza season and 11 nursing homes during the 1999-2000 influenza season in Niigata Prefecture, Japan.
                Six hundred ninety-nine residents and 440 healthcare workers (HCWs) during the first season, and 930 residents and 517 HCWs during the second season, with vaccination rates ranging from 0% to 97.7%.
                Overall, ILI decreased from 24.3% during the 1998-1999 season to 8.8% during the 1999-2000 season. Multivariate analysis adjusted for several factors, including gender, age, underlying diseases, and resident and HCW vaccination rates, failed to demonstrate clear individual protection of residents (relative risk [RR], 1.42; P = .2 for the first season; RR, 0.95; P = .9 for the second season). However, vaccination rates of 60% or greater for residents and HCWs reduced the risk of ILI, and also could prevent outbreaks during the 2 seasons. Highly impaired activities of daily living and chronic respiratory diseases were significantly associated with increased ILI.
                A high vaccination rate for both residents and HCWs may reduce the risk of ILI and institutional outbreaks in nursing homes. The failure of the 1982-1983 influenza vaccine to protect elderly NHCU residents from clinical infection with influenza A/Philippines/2/82 resulted primarily from antigenic drift of the epidemic strain, inasmuch as the attack rates in the vaccinated and nonvaccinated patients were not significantly different. This experience supports the decision to replace A/Bangkok/1/79 with A/Philippines/2/82 virus antigen in the 1983-1984 influenza vaccine. During the 1984-1985 influenza season, outbreaks of influenza A (H3N2) occurred in three Connecticut nursing homes. Influenza vaccination rates were 67% (96 out of 144), 35% (30 out of 85) and 69% (332 out of 483), respectively. The relative risk of illness for vaccinated compared to unvaccinated residents was 1.8 (95% confidence interval, 0.6, 5.9), 1.6 (95% confidence interval, 0.8, 3.0) and 1.1 (95% confidence interval, 0.8, 1.7) for each of the three nursing homes, respectively. In the third outbreak, 22 vaccinated residents without clinical illness had a geometric mean titer of hemagglutination-inhibition (HI) antibody of 20. Although low, this titer was significantly higher than that of nine unvaccinated residents without clinical illness (12, p less than .05); only three (14%) vaccinated residents had HI titers of greater than or equal to 40. These results suggest that levels of HI antibody in vaccinated residents were not protective at the time of the third outbreak, four to five months after vaccination. In general, the study of vaccine effectiveness in nursing homes is limited by sample size and statistical power. Despite these limits, the retrospective investigation of influenza outbreaks in nursing homes is often the only practical way to evaluate influenza vaccine effectiveness in the elderly on a yearly basis. An outbreak caused by influenza A/Philippines/2/82 (H3N2)-like viruses occurred in a partially vaccinated nursing home population in January 1985. During the first six days of the outbreak, 14 (25%) of 55 residents developed influenzalike illness. The risk of illness was most strongly associated with undetectable levels of antibody against the epidemic strain, with unvaccinated case-patients having more severe illnesses and a higher rate of hospitalization than vaccinated case-patients (5/8 vs 0/6). During the period of amantadine hydrochloride prophylaxis (100 mg/d) from days 7 to 35, only two (5%) of the remaining 41 residents became ill, even though 11 (27%) had no detectable antibody. Serum amantadine levels obtained on day 35 ranged from 117 to 737 ng/mL (mean 309 ng/mL), similar to therapeutic levels documented in younger adults who have taken the standard regimen of 200 mg/d; there were few clinically significant side effects. These findings illustrate the benefits of influenza vaccination and support the use of amantadine hydrochloride at a dosage of 100 mg daily for outbreak control among elderly persons. The effectiveness of influenza vaccination has been studied in an old age colony during the winters 1977-78 and 1978-79. The subjects, vaccinated and non-vaccinated, were submitted to continuous clinical and virological controls for about 6 months during the cold season. Three blood samples were obtained from the vaccinated subjects: 2 in November (before and after vaccination) and 1 in May of the following year. From the non-vaccinated 2 blood samples were obtained in November and May, respectively. The hemagglutino-inhibition test (HAI) permitted studying the serological response after vaccination, and verifying changes of the antibody titer to be related to influenza virus infections, contracted during the winter, which had escaped the clinico-virological detection. The serological response to the bivalent vaccine employed in November 1977 (A/Victoria/3/75 - 600 I.U.; B/Hong Kong/8/73 - 300 I.U.) was good for type A virus, and fair for B type. The low circulation of influenza virus, both among the 61 non-vaccinated and the 126 vaccinated subjects, during the following winter 1977-78 did not allow to arrive at any information on the vaccine protective efficacy. In autumn 1978 a trivalent vaccine had been employed, containing 300 I.U. of A/Texas/1/77, A/USSR/90/77, B/Hong Kong/8/73 viruses, respectively. During the following winter 1978-79, cases of infection, caused by type B/Hong Kong/5/72 - like influenza viruses were detected. The morbidity turned out significantly lower (P less than 0.05) in the vaccinated subjects (4 out of 140 cases) versus the non-vaccinated (7 out of 56 cases). The protection index supplied by the vaccine on such occasion was 77%. Influenza-related morbidity and mortality have been extensively studied with hospital and reimbursement data. However, little is known about the effectiveness of the annual vaccination programs in generally healthy community-dwelling elderly. The objective of our study was to investigate the effectiveness of influenza vaccination in community-dwelling elderly during the 1996 to 1997 influenza epidemic.
                We performed a population-based cohort study using the computerized Integrated Primary Care Information database in the Netherlands. Subjects who were 65 years and older in 1996 with a permanent status in a practice in the source population were considered eligible for study participation. Two cohorts were defined on the basis of vaccination status. We estimated and compared all-cause mortality, pneumonia, and clinical influenza infection rates between the cohorts.
                Influenza vaccination was associated with a significant reduction of morbidity and mortality in vaccinated elderly (relative risk [RR], 0.72; 95% confidence interval [CI], 0.60-0.87). Influenza infections decreased significantly in the vaccinated population (RR, 0.48; 95% CI, 0.26-0.91). Mortality was reduced significantly in elderly with comorbidity (RR, 0.67; 95% CI, 0.48-0.94). The risk reduction for pneumonia was nonsignificant (RR, 0.77; 95% CI, 0.55-1.07) but was temporally related to the peak influenza activity.
                In this study, influenza vaccination was associated with decreased mortality and influenza infections in community-dwelling elderly. Our results indicate that, in a season of mild influenza activity and good antigenic match between vaccine strains and circulating strains, influenza vaccination reduced mortality in the vaccinated population. Our data support an annual vaccination strategy for all community-dwelling elderly. The effectiveness of the influenza vaccine used in the 2001-2002 influenza season in Japan was investigated in a large-scale, geographically widely distributed, Internet-based study. Data were collected from 8841 of 9902 subjects registered by 38 clinics prior to the start of influenza season. Subjects were categorized into three groups by vaccination regimen: unvaccinated, vaccinated once, and vaccinated twice. Efficacy was also analyzed for three age groups: 0-15, 16-64, and 65-104 years. Influenza-like illness (ILI) was diagnosed according to Ministry of Health (MWH, Labor and Welfare in Japan) criteria. Laboratory-confirmed influenza cases were analyzed separately. The respective vaccine efficacy in the 0-15 years group for the one- and two-dose regimens was 67.6 and 84.5% for ILI and 54.0 and 79.8% for laboratory-confirmed influenza. Influenza vaccination was also shown to be effective in subjects 16-64 years. Vaccine effectiveness was not able to be determined for the over 65 years group, probably due to an insufficient number of infected patients. These results suggest that influenza vaccination is effective for children and adults and that a two-dose regimen is superior to a single dose in children 0-15 years. During the winter of 1989-1990, influenza type A(H3N2) circulated widely, causing excess morbidity and mortality nationwide. From November through April, 1989-1990, hospitalized cases of pneumonia and influenza occurring among noninstitutionalized individuals 65 or more years of age were identified by 20 acute care hospitals in southern lower Michigan. These cases were group matched on age, sex, race, and zip code to randomly sampled, community-based controls from a comprehensive listing of Medicare beneficiaries residing in the study area. Self-reported data were collected from cases and controls on influenza vaccine status for the 1989-1990 season and on a number of other factors which could have influenced vaccination status or outcome. Questionnaires were completed by 1,907 individuals, 449 of whom were cases, resulting in an overall response rate of 76%. A community-based influenza surveillance system was implemented to determine the timing and intensity of viral activity and influenza-like illness. Vaccine effectiveness in preventing overall pneumonia and influenza hospitalizations was estimated by logistic regression. During the 3-month period of surveillance-confirmed peak influenza type A(H3N2) circulation, vaccine effectiveness was 45% (95% confidence interval 14-64, p = 0.009). However, during the 3-month period of low or absent virus activity, identical methodology and model specification resulted in an effectiveness estimate of 21% that was not statistically different from zero (p = 0.36). The effectiveness determined during the peak period of virus circulation is felt to be a conservative estimate, since agents other than influenza are responsible for pneumonia and influenza hospitalizations, even during times of peak influenza activity. In 1999, all individuals > or = 65 yrs of age (n=258,754) in Stockholm County, Sweden, were offered influenza and pneumococcal vaccination in a prospective study on the effectiveness of these vaccines in reducing the need for hospital treatment and death due to influenza, pneumonia and invasive pneumococcal disease (IPD). Data on hospitalisation and mortality during 1 yr were obtained from the administrative database in Stockholm County Council. Vaccination was performed in 124,702 (48%) subjects; 72,107 had both vaccines, 29,346 only had the influenza vaccine and 23,249 only had the pneumococcal vaccine. Compared with the unvaccinated cohort, a lower incidence of hospitalisation for all endpoint diagnoses was seen in vaccinated persons. An additive effectiveness of vaccination was seen when both vaccines were given, with a reduction of hospital admissions for influenza (37%), pneumonia (29%) and IPD (44%). In-hospital mortality for pneumonia was significantly lower in those who received both vaccines, than in unvaccinated persons. To conclude, vaccination with influenza and pneumococcal vaccines together was effective in reducing the need for hospital admission for influenza and pneumonia. There was a strong indication that pneumococcal vaccination alone, was effective not only in the prevention of invasive pneumococcal disease, but also of pneumonia overall, although to a low degree. An ongoing surveillance program was intensified during the 1979-1980 and the 1980-1981 influenza seasons to determine whether an increased risk of acquiring Guillain-Barré syndrome (GBS) within eight weeks after influenza vaccination existed for adults in the United States who received influenza vaccine, when compared with adult who had not been vaccinated recently. Five hundred twenty-eight cases of GBS with onset between Sept 1 and March 31, including seven following recent vaccination, were reported by participating neurologists in 1979-1980; 459 cases, including 12 following recent vaccination, were reported in 1980-1981. The relative risk of acquiring GBS following influenza vaccination--0.6 in 1979-1980 and 1.4 in 1980-1981--was not significantly different from 1.0 in either season. These results suggest that there was no increased risk of acquiring GBS associated with the influenza vaccines administered during these seasons and that the causative "trigger agent" in the A/New Jersey (swine) influenza vaccine administered in 1976 has not been present in subsequent influenza vaccine preparations. nan Every winter, hospitals face a large increase in emergency respiratory admissions in elderly people. A case-control study was undertaken to assess the effect of routine influenza vaccine in preventing such admissions among a cohort of UK elderly presenting with acute respiratory illness during winter 2003-2004. 157 hospitalised cases and 639 controls (matched for age, sex and week of consultation) were interviewed. In a winter typical of levels of circulating influenza in recent years, influenza vaccine did not show a protective effect on emergency respiratory admissions overall (adjusted OR 1.2 (95%CI 0.8, 1.9). Policy makers should not rely solely on influenza vaccine routinely having a large effect on winter pressures, and should focus on additional preventive strategies. Influenza vaccine effectiveness evaluations were carried out among the elderly, as part of a demonstration established to estimate the value of including influenza vaccination as a covered Medicare benefit.
                Cases hospitalized with pneumonia and influenza-related diagnoses during November through April were identified and group matched to randomly selected community controls. Data were collected from cases and controls on influenza vaccination status and other factors which could have confounded the association between vaccination and hospitalization. A community-based influenza surveillance programme was conducted each year to determine the timing and aetiology of influenza activity. Logistic regression analyses were carried out to evaluate the association of influenza vaccination with the likelihood of hospitalization.
                In 1990-1991, during the peak of the influenza type B outbreak, influenza vaccination was estimated to be 31% (95% CI: 4-51%) effective in reducing the likelihood of hospitalization. In 1991-1992, during the peak of the influenza type A(H3N2) epidemic, a nearly identical point estimate for vaccine effectiveness was demonstrated (32%, 95% CI: 7-50%). Identical analyses carried out each year during the periods of low or absent influenza activity failed to demonstrate a significant effect for vaccination in preventing hospitalization.
                Results indicated that a significant benefit for vaccination could be expected during both type A and type B influenza seasons. To estimate the cost-effectiveness and net medical care costs of programs for annual influenza vaccinations for the elderly in a health maintenance organization (HMO).
                Population-based, case-control study.
                The Northwest Region of Kaiser Permanente, a prepaid group practice HMO in Portland, Oregon.
                Kaiser Permanente members 65 years of age and older who had at least 1 month of HMO eligibility during any of nine influenza seasons in the 1980s.
                The HMO's costs for providing medical care and conducting vaccination programs were estimated using accounting data.
                32% of high-risk elderly persons and 22% of non-high-risk elderly persons received influenza vaccinations. Aggregate vaccine effectiveness in preventing pneumonia and influenza hospitalizations was 30% (95% CI, 17% to 42%) for high-risk and 40% (CI, 1% to 64%) for non-high-risk elderly persons. The net savings to the HMO per vaccination was $6.11 for high-risk elderly persons and $1.10 for all elderly persons. The HMO incurred a net cost of $4.82 per vaccination for non-high-risk elderly persons.
                Influenza vaccination rates in this HMO were relatively low for high-risk elderly persons. The medical care costs saved by preventing pneumonia and influenza through vaccination of high-risk elderly persons provide a compelling rationale to increase compliance with recommendations for annual influenza vaccination. Indirect benefits, such as prevention of suffering, incapacity, and lost wages, are likely to compensate for the small net cost of vaccinating non-high-risk elderly persons. The aim of this study was to determine the cost effectiveness of influenza vaccination for healthy people aged 65-74 years living in the UK. People without risk factors for influenza (chronic heart, lung or renal disease, diabetic, immunosuppressed or those living in an institution) were identified from 20 general practitioner (GP) practices in Liverpool in September 1999. 729/5875 (12.4%) eligible individuals were recruited and randomised to receive either influenza vaccine or placebo (ratio 3:1), with all participants receiving 23-valent-pneumococcal polysaccharide vaccine unless already administered. The primary analysis was the frequency of influenza as recorded by a GP diagnosis of pneumonia or influenza like illness. In 2000, the UK vaccination policy was changed with influenza vaccine becoming available for all people aged 65 years and over irrespective of risk. As a consequence of this policy change, the study had to be fundamentally restructured and only results obtained over a one rather than the originally planned two-year randomised controlled trial framework were used. Results from 1999/2000 demonstrated no significant difference between groups for the primary outcome (relative risk 0.8, 95% CI 0.16-4.1). In addition, there were no deaths or hospitalisations for influenza associated respiratory illness in either group. The subsequent analysis, using both national and local sources of evidence, estimated the following cost effectiveness indicators: (1) incremental NHS cost per GP consultation avoided = 2000 pound sterling; (2) incremental NHS cost per hospital admission avoided = 61,000 pound sterling; (3) incremental NHS cost per death avoided = 1,900,000 pound sterling and (4) incremental NHS cost per QALY gained = 304,000 pound sterling. The analysis suggested that influenza vaccination in this population would not be cost effective. To describe the epidemiologic features of an outbreak of influenza A that occurred in a skilled nursing home although over 90 percent of the resident population had previously received influenza vaccine.
                Retrospective cohort study.
                Skilled nursing home facility in western New York State.
                Nursing home residents and patient-care staff.
                Incidence of influenza-like illness among vaccinated versus unvaccinated nursing home residents and staff.
                Thirty-seven of 124 residents (attack rate = 30%) and 18 of 146 staff (attack rate = 12%) had an influenza-like illness. Staff illness began 16 days prior to onset among residents. Six cases of pneumonia and three influenza-related deaths occurred, all among the vaccinated residents. Ninety percent of the nursing home residents and 10% of the staff received the influenza vaccine prior to the outbreak. The calculated vaccine efficacies were minus 21% and plus 45% for residents and staff, respectively.
                While antigenic drift of the circulating influenza virus was the major factor in the apparent vaccine failure, the observed poor staff immunization rate (10%) and absence of surveillance which precluded the use of amantadine chemoprophylaxis suggest that the use of these strategies may be of importance in controlling influenza outbreaks in nursing homes. To evaluate the use of influenza vaccine in nursing homes and its effectiveness in reducing the likelihood of influenza-like illness.
                A retrospective case-control study with active identification of influenza infection.
                All nursing homes in a seven-county study area in southern lower Michigan were eligible for participation. Analyses were based on data collected from 23 homes with documented influenza transmission.
                Persons aged 65 years or older who were residents of the nursing homes under study during the influenza type A(H3N2) outbreak in 1989-1990.
                Residents were identified as cases or controls based on occurrence of febrile respiratory illness meeting a case definition. Demographic and underlying illness information were gathered as were data on the use of influenza vaccine, antibiotics, and antivirals. Characteristics of the nursing homes were also recorded. Logistic regression analyses were carried out to determine vaccine effectiveness.
                Determinants of vaccine use were different from those observed in a parallel community-based study. In a multivariate model that considered the effects of resident and nursing home characteristics, vaccinated residents were significantly less likely than those who were not vaccinated to have an influenza-like illness (OR = .58 (95% CI, .43-.78), P < .001, imputed vaccine effectiveness estimate of 42%). Vaccination was more effective in younger residents (those aged 65 to 84) then in older residents (those older than 84 years).
                Influenza vaccination was effective in reducing the likelihood of influenza-like illness in nursing home residents. Effectiveness appeared to be related to age, which may function as a surrogate for related immunologic factors. Older nursing home residents should be targeted for newer vaccines and/or potential prophylactic use of antivirals. The effectiveness of influenza vaccination against hospitalization and death can only ethically be assessed in observational studies. A concern is that individuals who are vaccinated are healthier than individuals who are not vaccinated, potentially biasing estimates of effectiveness upward.
                We conducted a historical cohort study of individuals >64 years of age, for whom there were data available in the General Practice Research Database for 1989 to 1999 in England and Wales. Rates of admissions for acute respiratory diseases and rates of death due to respiratory disease were compared over 692,819 person-years in vaccine recipients and 1,534,280 person-years in vaccine nonrecipients.
                The pooled effectiveness of vaccine against hospitalizations for acute respiratory disease was 21% (95% confidence interval [CI], 17%-26%). The rate reduction attributable to vaccination was 4.15 hospitalizations/100,000 person-weeks in the influenza season. Among vaccine recipients, no important reduction in the number of admissions to the hospital was seen outside influenza seasons. The pooled effectiveness of vaccine against deaths due to respiratory disease was 12% (95% CI, 8%-16%). A greater proportionate reduction was seen among people without medical disorders, but absolute rate reduction was higher in individuals with medical disorders, compared with individuals without such disorders (6.14 deaths due to respiratory disease/100,000 person-weeks vs. 3.12 deaths due to respiratory disease/100,000 person-weeks). Clear protection against death due to all causes was not seen.
                Influenza vaccination reduces the number of hospitalizations and deaths due to respiratory disease, after correction for confounding in individuals >64 years of age who had a high risk or a low risk for influenza. For elderly people, untargeted influenza vaccination is of confirmed benefit against serious outcomes. From December 10, 1982, to March 4, 1983, when influenza A (H3N2) viruses circulated in Michigan, outbreaks of influenza-like illness were identified in seven nursing homes in Genesee County; 272 (27%) of 1,018 residents were affected. Unvaccinated residents were more likely than vaccinated residents to become ill (risk ratio [RR], 2.6; 95% confidence interval [Cl], 1.8-3.6) and were subsequently more likely to be hospitalized (RR, 2.4; 95% Cl, 1.2-4.8), develop roentgenographically proven pneumonia (RR, 2.9; 95% Cl, 1.6-5.3), or die (RR, 5.6; 95% Cl, 1.2-9.1). Similar observations were made during investigations in six of the eight remaining nursing homes in Genesee County, in which 57 (12%) of 458 residents became ill sporadically. These findings suggest that influenza vaccine can reduce the incidence and severity of influenza virus infections among the elderly and chronically ill and underscore the importance of vaccination programs for those in nursing homes and in the general community. Vaccination rates for healthy senior citizens are lower than those for senior citizens with underlying medical conditions such as chronic heart or lung disease. Uncertainty about the benefits of influenza vaccination for healthy senior citizens may contribute to lower rates of utilization in this group.
                To clarify the benefits of influenza vaccination among low-risk senior citizens while concurrently assessing the benefits for intermediate- and high-risk senior citizens.
                All elderly members of a large health maintenance organization were included in each of 6 consecutive study cohorts. Subjects were grouped according to risk status: high risk (having heart or lung disease), intermediate risk (having diabetes, renal disease, stroke and/or dementia, or rheumatologic disease), and low risk. Outcomes were compared between vaccinated and unvaccinated subjects after controlling for baseline demographic and health characteristics.
                There were more than 20000 subjects in each of the 6 cohorts who provided 147551 person-periods of observation. The pooled vaccination rate was 60%. There were 101 619 person-periods of observation for low-risk subjects, 15 482 for intermediate-risk, and 30 450 for high-risk subjects. Vaccination over the 6 seasons was associated with an overall reduction of 39% for pneumonia hospitalizations (P<.001), a 32% decrease in hospitalizations for all respiratory conditions (P<.001), and a 27% decrease in hospitalizations for congestive heart failure (P<.001). Immunization was also associated with a 50% reduction in all-cause mortality (P<.001). Within the risk subgroups, vaccine effectiveness was 29%, 32%, and 49% for high-, intermediate-, and low-risk senior citizens for reducing hospitalizations for pneumonia and influenza (for high and low risk, P< or =.002; for intermediate risk, P = .11). Effectiveness was 19%, 39%, and 33% (for each, P< or =.008), respectively, for reducing hospitalizations for all respiratory conditions and 49%, 64%, and 55% for reducing deaths from all causes (for each, P<.001). Vaccination was also associated with direct medical care cost savings of $73 per individual vaccinated for all subjects combined (P = .002). Estimates of cost savings within each risk group suggest that vaccination would be cost saving for each subgroup (range of cost savings of $171 per individual vaccinated for high risk to $7 for low risk), although within the subgroups these findings did not reach statistical significance (for each, P> or =.05).
                This study confirms that healthy senior citizens as well as senior citizens with underlying medical conditions are at risk for the serious complications of influenza and benefit from vaccination. All individuals 65 years or older should be immunized with this vaccine. The immunogenicity and efficacy of Russian live attenuated and US inactivated trivalent influenza vaccines administered alone or in three different combinations were evaluated in a randomized, placebo-controlled, double-blinded study of 614 elderly or chronically ill nursing home residents in St. Petersburg, Russia during the 1996-97 influenza season. Postvaccination serum antibody responses were more frequent among individuals administered the combination vaccines than among those vaccinated with live or inactivated vaccine alone. Only individuals who received live vaccine, alone or in combination with inactivated vaccine, achieved significant postvaccination increases in virus-specific nasal IgA. Efficacy in preventing laboratory-confirmed influenza in vaccinated versus nonvaccinated individuals was 67% (95%CI, 36-81%) for recipients of a combination of the vaccines compared with 51% (95%CI, -17-79%) for recipients of live vaccine alone and 50% (95%CI, -26-80%) for recipients of inactivated vaccine alone. These results suggest that administration of a combination of influenza vaccines may provide a strategy for improved influenza vaccination of elderly people. nan A study was carried out in Newcastle to assess responses to influenza vaccines in elderly nursing home patients and in younger adults during 1983 and 1984. The decision to vaccinate the elderly subjects was made by their general practitioners. A concurrent randomized placebo-controlled trial of the same vaccine was performed in young adult volunteers. Elderly subjects generally possessed higher levels of pre-existing antibody to the influenzal haemagglutinins that were present in the vaccines than did younger subjects. The highest levels were observed in the 52-63 years' age group. Younger subjects showed significantly greater responses to vaccines compared with elderly subjects (P less than 0.05). Peak responses were noted in the 16-24 years' age group. Of a total of 326 elderly subjects (70% of whom had been vaccinated), six participants, two of whom had been vaccinated, contracted laboratory-proven influenza during 1983. Only one unvaccinated subject of a total of 365 subjects (50% of whom had been vaccinated) contracted influenza during 1984. In both years illness was produced by strain A/Philippines/2/82. An outbreak of influenza A in nursing home residents is reported and other studies of influenza vaccine effectiveness in elderly populations are reviewed. The outbreak occurred in a Los Angeles nursing home between February and March 1983. Of the 87 residents, 46 (53%) were affected with influenza-like illness. Attack rates were similar between immunized and unimmunized residents (52% versus 58%), and yielded a vaccine effectiveness estimate of 10%. No additional protection could be demonstrated in residents who received vaccine for two consecutive years. Seven persons died (mortality rate of 8.1%); the mortality rate was greater in the unimmunized (15.8%) than in the immunized (6.2%). Because this study and other field studies of influenza vaccine are limited in precision and power, a statistical summary of the various studies was constructed. Summarizing the studies of institutionalized elderly (in hospitals and nursing and retirement homes) yielded an estimate of 74% for the average vaccine effectiveness in mortality reduction, and an estimate of 33% for the average effectiveness in preventing clinical illness. For the non-institutionalized elderly, the corresponding estimates were 47% for mortality, and 5% for clinical illness. Despite the obvious limitations of such summaries, it seems reasonable to conclude that influenza vaccines have on the average been of clear benefit in the institutionalized elderly, while the benefits in the non-institutionalized elderly have been less dramatic and may warrant further investigation. To estimate the effectiveness of influenza vaccine in preventing hospital admission for pneumonia in non-institutionalised elderly people.
                This was a case-control study.
                All three public hospitals in the Castellón area of Spain.
                Cases were people aged 65 or more not living in an institution who were admitted to hospital for pneumonia between November 15, 1994 and March 31, 1995. Each case was matched with two sex matched control subjects aged 65 years or older admitted to hospital in the same week for acute abdominal surgical conditions or trauma. The sampling of incident cases was consecutive. Eighty three cases and 166 controls were identified and included in the study.
                Trained interviewers completed a questionnaire for each subject on the vaccination status, smoking habits, previous diseases, health care use, social contacts, family background, the vaccination status of the family carer, home characteristics, and socioeconomic status.
                The adjusted odds ratio of the influenza vaccination preventing admission to hospital for pneumonia was 0.21 (95% confidence interval 0.09, 0.55). The variables which best explained the risk of being a case were age, intensity of social contacts, health care use, previous diseases, and the existence of a vaccinated family carer.
                Influenza vaccination reduced significantly hospital admissions for pneumonia in non-institutionalised elderly people. In a prospective study of community-dwelling people 60-90 years of age, we examined the coverage of influenza vaccine during 1992-3 and 1993-4, the efficacy of vaccination in reducing serologically-confirmed clinical episodes of influenza A during 1993, and the effect of cigarette smoking. During 1992 and 1993, influenza vaccine was given to 106/215 (49%) and 120/204 (59%) people with risk conditions, and 84/225 (37%) and 103/235 (44%) without risk conditions. Influenza vaccination and general practitioner consultations during 1992 were independent predictors of vaccination in 1993, but current smoking was a negative predictor. Of 209 unimmunized people, 8/35 (23%) smokers had clinical influenza as compared with 11/174 (6%) non-smokers (OR 4.4, 95% CI 1.6 to 11.9). Of 371 non-smokers, 1/197 (0.5%) vaccinees had influenza as compared with 11/174 (6%) non-vaccinees (OR 0.075, 95% CI 0.587 to 0.009). No cases of influenza occurred among 21 current smokers who were vaccinated. The effectiveness of immunization against influenza in elderly persons is uncertain. A retrospective cohort study in a New York City nursing home examined the occurrence of pneumonia and its related mortality over three consecutive influenza seasons (Nov 1 through April 30, 1979 to 1980, 1980 to 1981, and 1981 to 1982). Nearly one half of approximately 450 residents (mean age, 84 years) accepted immunization each year. The vaccinated and unvaccinated groups were similar. The attack rate of pneumonia did not differ significantly between the vaccinated and unvaccinated groups in any of the three influenza seasons. When influenza was occurring in the community (1979 to 1980 and 1980 to 1981), however, the risk of death from pneumonia in the unvaccinated group was three-fold higher than in the vaccinated group (60% vs 18% and 73% vs 25%, respectively). In a year when influenza was specifically sought and not found in the facility (1981 to 1982), however, vaccination did not affect pneumonia-related mortality. This study also suggests that estimates of mortality due to pneumonia should include deaths that occur up to 60 days after onset of pneumonia; shorter follow-up may overestimate the protective effect of vaccination. The effectiveness of influenza vaccine in reducing hospital admissions for pneumonia, influenza, bronchitis, or emphysema was assessed by a case-control study of people aged 16 years and older who were admitted to 10 Leicestershire hospitals between 1 December 1989 and 31 January 1990. Hospital and general practitioners' records for 156 admissions (the cases) and 289 controls matched for age and sex were reviewed. Information was collected on demography, the usual place of residence (institutional or non-institutional), the existence of chronic illness, and vaccination during the 5 years before admission. The odds ratio for hospital admission among vaccinees was 0.67 (95% CI 0.39-1.12) giving an estimate of vaccine effectiveness in this setting of 33% (95% CI 0-61). However, multivariate logistic regression, adjusting for the effects of institutional care and chronic illness, revealed that influenza vaccination reduced hospital admissions by 63% (95% CI 17-84%). There was a strong trend towards improved vaccine effectiveness when used in institutional settings. Influenza vaccine is effective in reducing hospital admissions for influenza, pneumonia, bronchitis and emphysema, and effectiveness is comparable to that observed for influenza and pneumonia admissions in North America. Influenza epidemics are associated with excess winter mortality. Risk factors for influenza complications and death include chronic illness and living in residential care. In the UK uptake of influenza vaccine among high-risk groups is only 10-40%, partly because of scepticism about vaccine efficacy. We have assessed the efficacy of influenza vaccine in reducing mortality from certified influenza by a case-control study of subjects aged 16 years or older who died between Nov 4, 1989, and Feb 23, 1990, in 36 district health authorities in England. We reviewed general practitioners' records for 315 patients who died of influenza and 777 controls, matched for age, sex, and area of residence, who died a year after the epidemic. Information was collected on demography, the usual place of residence (institutional or noninstitutional), and the existence of chronic illness. Conditional logistic regression analysis for matched case-control studies showed that influenza vaccination reduced mortality by 41% (95% CI 13-60) for all subjects. Further adjustments showed that among subjects who received the vaccine for the first time in 1989, vaccination reduced mortality by 9% (0-59); however, among those who had also been vaccinated previously, mortality was reduced by 75% (31-91). We detected no significant differences in the effect of vaccine between subjects who lived in institutions and in the community (p = 0.16), or between subjects with high-risk medical conditions and those without (p = 0.76). Influenza vaccine is effective in reducing mortality from influenza, and efficacy seems to be greater after repeated annual vaccination than after first administration. The reactogenicities and immunogenicities of two influenza virus vaccines were compared in a placebo-controlled clinical trial among healthy ambulatory persons > or = 65 years old (mean age, 72 years). Volunteers were assigned randomly to receive 15-, 45-, or 135-micrograms doses of monovalent influenza A/Taiwan (H1N1) hemagglutinin (HA) or subvirion (SV) vaccine intramuscularly or a placebo. Increasing doses of SV vaccine were associated with a higher rate of injection site discomfort (P < 0.05; chi-square test for linear trend), but all doses of both vaccines were well tolerated. Increasing the dose of the HA or the SV vaccine resulted in increasingly higher postimmunization levels of serum hemagglutination inhibition and neutralizing antibody levels (P < 0.001; multiple linear regression). Mean serum antibody titers at 1 month increased two- to threefold with a ninefold increase in dose; the frequencies of fourfold or greater rises in titer likewise increased. An increase in the dose of the HA or the SV vaccine also resulted in increased frequencies of rises in immunoglobulin A or G antibody titers in nasal wash specimens. The frequencies increased approximately twofold for each vaccine with a ninefold increase in the dose. These data suggest that increasing the HA vaccine dose is a promising approach to the development of improved influenza virus vaccines for use in elderly people. nan The safety and immunogenicity of two recent cold-adapted reassortant influenza B viruses were evaluated in persons at high risk for influenza-related morbidity and mortality. Ambulatory adults > 65 years old or with chronic high-risk conditions were randomly assigned to receive parenteral trivalent inactivated influenza vaccine containing either influenza B/Ann Arbor/86 or B/Yamagata/88 hemagglutinin antigens, cold-adapted reassortant influenza B/Ann Arbor/1/86 or B/Yamagata/16/88 viruses (10(7.2) TCID50), or placebo in double-blind fashion. Cold-adapted vaccine viruses were well tolerated, with similar rates of respiratory symptoms in all groups. There were no changes in spirometry or oxygen saturation following vaccination. Immune responses to both types of vaccine were modest, with serum antibody responses occurring significantly more frequently and with higher magnitude in those receiving inactivated than in those receiving cold-adapted vaccine. Cold-adapted, reassortant influenza B vaccines are safe in the elderly and those with chronic illness but are not optimally immunogenic in this group. To assess the frequency and type of side effects after influenza vaccination in elderly people.
                Randomised double blind placebo controlled study.
                15 general practices in the southern Netherlands.
                1806 patients aged 60 or older, of whom 904 received influenza vaccine and 902 placebo.
                Adverse reactions reported on postal questionnaire completed four weeks after vaccination.
                210 (23%) patients given vaccine reported one or more adverse reactions compared with 127 (14%) given placebo. The frequency of local adverse reactions were 17.5% in the vaccine group and 7.3% in the placebo group (p < 0.001). There was no difference in systemic adverse reactions (11% v 9.4%; p = 0.34). In general, men reported fewer side effects than women.
                Only local side effects were more common in vaccinated patients and all side effects were mild. To determine the efficacy of influenza vaccination in elderly people.
                Randomized double-blind placebo-controlled trial.
                Fifteen family practices in the Netherlands during influenza season 1991-1992.
                A total of 1838 subjects aged 60 years or older, not known as belonging to those high-risk groups in which vaccination was previously given.
                Purified split-virion vaccine containing A/Singapore/6/86(H1N1), A/Beijing/353/89(H3N2), B/Beijing/1/87, and B/Panama/45/90 (n = 927) or intramuscular placebo containing physiological saline solution (n = 911).
                Patients presenting with influenzalike illness up to 5 months after vaccination; self-reported influenza in postal questionnaires 10 weeks and 5 months after vaccination; serological influenza (fourfold increase of antibody titer between 3 weeks and 5 months after vaccination).
                The incidence of serological influenza was 4% in the vaccine group and 9% in the placebo group (relative risk [RR], 0.50; 95% confidence interval [CI], 0.35 to 0.61). The incidences of clinical influenza were 2% and 3%, respectively (RR, 0.53; 95% CI, 0.39 to 0.73). The effect was strongest for the combination of serological and clinical influenza (RR, 0.42; 95% CI, 0.23 to 0.74). The effect was less pronounced for self-reported influenza.
                In the elderly, influenza vaccination may halve the incidence of serological and clinical influenza (in periods of antigenic drift). nan nan To evaluate the effectiveness and possible cost savings of influenza vaccination.
                Members age 65 and older in a Medicare managed care plan during the 1994-1995, 1995-1996, and 1996-1997 influenza seasons.
                The study examined administrative data on influenza vaccination and subsequent hospitalizations. Outcomes included hospitalization with pneumonia or influenza, with any respiratory condition, and with congestive heart failure (CHF).
                Vaccinated subjects experienced fewer hospitalizations with respiratory conditions or CHF than had unvaccinated subjects (OR=0.8 (95% CI, 0.7, 0.9) in analyses adjusted for age, sex, pneumococcal vaccination, health utilization, and morbidity). Analyses adjusted in addition for ethnicity obtained similar results among the subgroup of members whose ethnicity was known. Subjects without major disease in the previous 12 months had lower odds ratios for vaccination than subjects with major disease (OR values of 0.5 [95% CI, 0.4, 0.7] and 0.9 [95% CI, 0.8, 1.1], respectively). Subjects ages 65 to 79 had lower odds ratios for vaccination than subjects ages 80 and older (OR values of 0.7 [95% CI, 0.6, 0.9] and 0.9 [95% CI, 0.8, 1.1], respectively). Estimated cost savings averaged about $80 per vaccinated subject.
                Subjects ages 65 to 79 who had received influenza vaccination experienced fewer hospitalizations and had lower costs than had unvaccinated subjects. Associations were weaker for subjects age 80 and older. The results, consistent with recommendations for the use of influenza vaccine, suggest that people ages 65 to 79 should be heavily targeted for vaccination. nan Concern about side effects constitutes a major deterrent to patient compliance with influenza vaccination, yet there is a paucity of data about the occurrence of adverse reactions in the population targeted for immunization. We conducted a randomized, double-blind, crossover trial to compare the frequency of adverse reactions following administration of 1988-1989 trivalent split-antigen influenza vaccine and saline placebo. Outpatient veterans 65 years of age or over (n = 336) were recruited by mail and were randomly assigned to receive vaccine followed 2 weeks later by placebo injection or placebo followed 2 weeks later by vaccine. There was no significant difference between influenza vaccine and placebo with respect ot the proportion of subjects reporting disability or systemic symptoms. This serial cohort study assessed the risk of hospitalization or death associated with influenza and the effectiveness of influenza vaccination among subgroups of elderly members of 3 managed-care organizations in the United States. Data on baseline characteristics and outcomes were obtained from computerized databases. A total of 122,974 (1996-1997 season) and 158,454 (1997-1998 season) persons were included in the cohorts. Among unvaccinated persons, hospitalizations for pneumonia/influenza or death occurred in 8.2 of 1000 healthy and 38.4 of 1000 high-risk persons in year 1, and in 8.2 of 1000 healthy and 29.3 of 1000 high-risk persons in year 2. After adjustments, vaccination was associated with a 48% reduction in the incidence of hospitalization or death (95% confidence interval [CI], 42-52) in year 1 and 31% (95% CI, 26-37) in year 2. Effectiveness estimates were statistically significant and generally consistent across the healthy and high-risk subgroups. The absolute risk reduction, however, was 2.4- to 4.7-fold higher among high-risk than among healthy elderly persons. All elderly individuals may substantially benefit from vaccination. However, the impact of influenza is greater in persons with high-risk medical conditions. Upper respiratory tract illnesses have been associated with an increased risk of morbidity and mortality.
                To assess the influence of vaccination against influenza on the risk of hospitalization in internal medicine and geriatric wards, and the risk of death from all causes during the 2000-2001 influenza season.
                A historical cohort study was conducted using computerized general practitioner records on patients aged 65 years and above, members of "Maccabi Healthcare Services"--the second largest health maintenance organization in Israel with 1.6 million members. The patients were divided into high and low risk groups corresponding to coexisting conditions, and were studied. Administrative and clinical data were used to evaluate outcomes.
                Of the 84,613 subjects in the cohort 42.8% were immunized. At baseline, vaccinated subjects were sicker and had higher rates of coexisting conditions than unvaccinated subjects. Vaccination against influenza was associated with a 30% reduction in hospitalization rates and 70% in mortality rates in the high risk group. The NNT (number needed to treat) measured to prevent one hospitalization was 53.2 (28.2 in the high risk group and 100.4 in the low risk group). When referring to length of hospitalization, one vaccine was needed to prevent 1 day of hospitalization among the high risk group. Analyses according to age and the presence or absence of major medical conditions at baseline revealed similar findings across all subgroups.
                In the elderly, vaccination against influenza is associated with a reduction in both the total risk of hospitalization and in the risk of death from all causes during the influenza season. These findings compel the rationale to increase compliance with recommendations for annual influenza vaccination among the elderly. We prospectively studied the efficacy of influenza vaccine during an influenza A/Arizona/80 (H3N2) outbreak at the Jewish Home and Hospital for the Aged in New York in the winter season of 1982 to 1983. All patients had been offered influenza vaccine before the outbreak; 181 chose to be vaccinated and 124 refused vaccination but agreed to participate in the study. Among those with serologic evidence of influenza infection, respiratory illness was significantly more common in the unvaccinated group (six of 14 vs one of 22). The overall mortality was 13 (7.2%) of 181 in the vaccinated group and 22 (17.7%) of 124 in the control group. The vaccinated and the control groups were examined for comparability. A logistic regression analysis, which controlled for differences in sex and level of nursing care, indicated that the difference in mortality was still significant, with a summary odds ratio of 2.7. The relative risk of death in the unvaccinated group was comparable at 2.18. Influenza vaccine reduced the mortality by 59% in the vaccinated group compared with the control group. This study developed methods and determined the impact of influenza vaccination on elderly persons in 3 large health plans: Kaiser Permanente Northwest, HealthPartners, and Oxford Health Plans. Data for the 1996-1997 and 1997-1998 seasons were extracted from administrative databases. Subjects were health plan members > or = 65 years old. Comorbid conditions collected from the preceding year were used for risk adjustment with logistic regression. The virus-vaccine match was excellent for year 1 and fair for year 2. Both years, during peak and total periods, vaccination reduced all causes of death and hospitalization for pneumonia and influenza: hospitalizations were reduced by 19%-20% and 18%-24% for years 1 and 2, respectively, and deaths were reduced by 60%-61% and 35%-39% for the same periods. These results show that all elderly persons should be immunized annually for influenza. The methods used in this study are an efficient cost-effective way to study vaccine impact and similar questions. The number of reports of influenza-vaccine-associated Guillain-Barré syndrome to the national Vaccine Adverse Event Reporting System increased from 37 in 1992-1993 to 74 in 1993-1994, arousing concern about a possible increase in vaccine-associated risk.
                Patients given a diagnosis of the Guillain-Barré syndrome in the 1992-1993 and 1993-1994 influenza-vaccination seasons were identified in the hospital-discharge data bases of four states. Vaccination histories were obtained by telephone interviews during 1995-1996 and were confirmed by the vaccine providers. Disease with an onset within six weeks after vaccination was defined as vaccine-associated. Vaccine coverage in the population was measured through a random-digit-dialing telephone survey.
                We interviewed 180 of 273 adults with the Guillain-Barré syndrome; 15 declined to participate, and the remaining 78 could not be contacted. The vaccine providers confirmed influenza vaccination in the six weeks before the onset of Guillain-Barré syndrome for 19 patients. The relative risk of the Guillain-Barré syndrome associated with vaccination, adjusted for age, sex, and vaccine season, was 1.7 (95 percent confidence interval, 1.0 to 2.8; P=0.04). The adjusted relative risks were 2.0 for the 1992-1993 season (95 percent confidence interval, 1.0 to 4.3) and 1.5 for the 1993-1994 season (95 percent confidence interval, 0.8 to 2.9). In 9 of the 19 vaccine-associated cases, the onset was in the second week after vaccination, all between day 9 and day 12.
                There was no increase in the risk of vaccine-associated Guillain-Barré syndrome from 1992-1993 to 1993-1994. For the two seasons combined, the adjusted relative risk of 1.7 suggests slightly more than one additional case of Guillain-Barré syndrome per million persons vaccinated against influenza. The effectiveness of influenza and pneumococcal vaccination in the prevention of hospital admissions and death has not been assessed prospectively. We have therefore examined the effects of influenza and pneumococcal vaccination in individuals aged 65 years and older in a 3-year prospective study, between Dec 1, 1998 and May 31, 1999.
                All individuals in Stockholm County aged 65 years or older (259,627) were invited to take part in a vaccination campaign against influenza and pneumococcal infection. We recorded for all vaccine recipients (100,242) name, and date of birth, and whether they had been given both or one of the vaccines. All individuals (> or = 65 years) admitted to hospital in Stockholm County with influenza and pneumonia related diagnoses were identified between Dec 1, 1998, and May 31, 1999.
                The incidence (per 100,000 inhabitants per year) of hospital treatment was lower in the vaccinated than in the unvaccinated cohort for all diagnoses: 263 versus 484 (-46% [95% CI 34-56]) for influenza; 2199 versus 3097 (-29% [24-34)) for pneumonia; 64 versus 100 (-36% [3-58]) for pneumococcal pneumonia; and 20 versus 40 (-52% [1-77]) for invasive pneumococcal disease. The total mortality was 57% (55-60) lower in vaccinated than in unvaccinated individuals (15.1 vs 34.7 deaths per 1000 inhabitants).
                These findings show that general vaccination leads to substantial health benefits and to a reduction of mortality from all causes in this age group. To characterize risk factors for outbreak-associated influenza illness and death in a nursing home.
                Outbreak investigation with predetermined and concurrently determined risk information.
                A nursing home service in a multiward chronic care hospital, Honolulu, Oahu, 1989 to 1990.
                Elderly nursing home patients receiving long-term care.
                Influenza vaccination, amantadine administration, and infection control measures.
                Neither routine infection control measures nor vaccination prevented illness, complications, or death in a nursing home outbreak of influenza A. The 55% case-fatality rate resulted from severe pneumonia. Influenza transmission may have been mediated by staff via either contaminated hands or fomites.
                Data from this and other outbreaks suggest that recommendations for preventing nosocomial influenza in the nation's 1.5 million nursing home residents should be reconsidered. An explosive outbreak of Influenza A (H3N2) occurred during early February 1985 among the 55 residents of a nursing home in Douglas, Wyoming. Thirty of the 55 (55%) had febrile respiratory illnesses. Thirty-six (65%) had received influenza vaccine. The attack rate was 84% in unvaccinated and 39% in vaccinated persons. Vaccine efficacy was estimated to be 54%. There were eight cases of pneumonia in unvaccinated and four in vaccinated persons, three deaths in unvaccinated and one death in vaccinated persons. Complement fixation and hemagglutination inhibition tests on sera from 47 residents confirmed the diagnosis of Influenza A in the great majority of individuals, and furthermore showed very low levels of antibody for the Influenza A H1N1 and Influenza B components of the vaccine. To assess the clinical effectiveness of influenza vaccination in preventing influenza-associated hospitalization and death.
                Case-control study.
                Noninstitutionalized persons aged 45 years or older living in Manitoba, on December 1, 1982, and December 1, 1985.
                Linked records of the Manitoba population registry, hospital-discharge abstracts, physician claims for ambulatory-patient visits and influenza vaccination, and vital statistics were used. A matched-set analysis estimated the clinical effectiveness of influenza vaccination in preventing hospital admissions and deaths from influenza-associated conditions during influenza A (H3N2) outbreak periods in 1982 to 1983 (12 weeks) and 1985 to 1986 (10 weeks). The analysis adjusted for hospital discharge and ambulatory care for high-risk conditions within the previous 15 months and 3 months, respectively.
                Influenza vaccination prevented 32% to 39% of hospital admissions with pneumonia and influenza and 15% to 34% of admissions with all respiratory conditions. Vaccination was 43% to 65% effective in preventing hospital deaths with these conditions (all listed diagnoses) and 27% to 30% effective in preventing deaths from all causes.
                Influenza vaccination has substantial clinical effectiveness in preventing hospital admission and death from influenza-associated conditions in noninstitutionalized individuals. nan nan Describe an outbreak of influenza A (H3N2); provide an analysis of vaccine efficacy; measure the sensitivity, specificity, and positive predictive value of 3 clinical case definitions of influenza.
                A nursing home in Washington County, Maryland. The outbreak involved 52 residents (attack rate = 47.7%) and at least 10 of 140 employees (minimum attack rate = 7.1%).
                Twenty-five residents exhibited a 4-fold or greater increase in titer to influenza A/Sichuan/2/87. Vaccine efficacy was measured at -7.1%, suggesting that the influenza vaccine in 1988/1989 did not offer optimal protection against influenza A infection for the institutionalized elderly.
                The outbreak was a clear indicator of the need for rapid diagnosis. With the use of rapid diagnostic tests, influenza A could have been detected in time to use amantadine. Outbreaks of influenza in nursing homes still occur, even when a large portion of residents have been inoculated with inactivated vaccine. Data were collected in 1991--1992 from 83 eligible skilled nursing homes located in southern Lower Michigan to determine the effectiveness of inactivated influenza vaccine in preventing influenza-like illness and influenza-associated pneumonia. Surveillance was conducted to identify the occurrence of influenza in the homes and, at the end of the season, specific data were gathered on all residents of homes with influenza activity. Age- and sex-adjusted estimates of vaccine effectiveness were calculated using Cox proportional hazards models for each nursing home. Estimates were pooled using precision-based weights calculated from data for each home. Vaccine was found to be 33% effective in preventing total respiratory illness (influenza-like illness and clinically diagnosed pneumonia). In prevention of pneumonia alone, vaccine was 43% effective. The estimate for prevention of pneumonia rose to 55% if the period under consideration was limited to the time of peak influenza activity. Given the number of eligible homes and the cohort methodology used, the results support continuation of current policy, encouraging use of vaccine in all nursing home residents. Despite recommendations for annual vaccination against influenza, more than half of elderly Americans do not receive this vaccine. In a serial cohort study, we assessed the efficacy and cost effectiveness of influenza vaccine administered to older persons living in the community.
                Using administrative data bases, we studied men and women over 64 years of age who were enrolled in a large health maintenance organization in the Minneapolis-St. Paul area. We examined the rate of vaccination and the occurrence of influenza and its complications in each of three seasons: 1990-1991, 1991-1992, and 1992-1993. Outcomes were adjusted for age, sex, diagnoses indicating a high risk, use of medications, and previous use of health care services.
                Each cohort included more than 25,000 persons 65 years of age or older. Immunization rates ranged from 45 percent to 58 percent. Although the vaccine recipients had more coexisting illnesses at base line than those who did not receive the vaccine, during each influenza season vaccination was associated with a reduction in the rate of hospitalization for pneumonia and influenza (by 48 to 57 percent, P < or = 0.002) and for all acute and chronic respiratory conditions (by 27 to 39 percent, P < or = 0.01). Vaccination was also associated with a 37 percent reduction (P = 0.04) in the rate of hospitalization for congestive heart failure during the 1991-1992 season, when influenza A was epidemic. The costs of hospitalization for all types of illness studied were lower in the vaccinated group during 1991-1992 (range of reduction, 47 to 66 percent; P < 0.005) and for acute and chronic respiratory conditions and congestive heart failure in 1990-1991 (reductions of 37 percent and 43 percent, respectively; P < or = 0.05). Direct savings per year averaged $117 per person vaccinated (range, $21 to $235), with cumulative savings of nearly $5 million. Vaccination was also associated with reductions of 39 to 54 percent in mortality from all causes during the three influenza seasons (P < 0.001).
                For elderly citizens living in the community, vaccination against influenza is associated with reductions in the rate of hospitalization and in deaths from influenza and its complications, as compared with the rates in unvaccinated elderly persons, and vaccination produces direct dollar savings. Case-control study designed to determine the effectiveness of an MF59-adjuvanted influenza vaccine in the population aged 65 years and older living in the community. Detailed health histories were obtained on both cases and controls that included a functional measure of co-morbidity (Barthel Index). Subjects were all eligible persons admitted to various hospitals with a diagnosis of pneumonia during the winter months and were matched by sex, hospital and admission week to controls admitted for non-medical reasons. The influenza vaccination programme using the MF59-adjuvanted influenza vaccine significantly reduced the probability of being hospitalised for pneumonia in the elderly over 64 years of age, even in a season with a low influenza activity, during which the predominant circulating strains were types B and A (H1N1). To evaluate the effectiveness of anti-flu vaccination on elderly people not in institutions, by measuring its effect on the reduction of deaths and hospital admissions due to Cardio-respiratory failure.
                A retrospective cohort.
                La Chana Health Centre, Granada.
                1,965 elderly people who were seen at the Health Centre over the previous three years.
                779 elderly people (39.6%) were vaccinated. 35 were admitted to hospital with Cardio-respiratory failure and 59 died. Of these two groups, 13 and 23 respectively had been given the anti-flu vaccination that year. After checking for variables which could lead to confusion, the vaccine was shown to be effective both in reducing admissions (advantage ratio 1,330) and deaths (advantage ratio 1,221).
                Given the effectiveness of anti-flu vaccinations, active efforts to encourage non-institutionalised elderly people to be vaccinated should be increased. Assess the effectiveness of influenza vaccination in reducing hospitalization due to pneumonia and influenza among elderly subjects in a community in central Italy. Estimate the hospitalization fraction preventable by extending the vaccination program.
                Case-control study. Cases were subjects aged 65+ at hospital admission (1 December 1994-31 March 1995). For each case two population controls were randomly chosen, matched by sex, age and residence. Variables of interest were recorded through a postal questionnaire and telephone interview. A matched-set analysis was carried out adjusting for concomitant chronic diseases, education, type of home heating, and smoking habits. The preventable fraction of hospitalization was computed through the application of the attributable risk estimate. The setting was 33 municipalities in central Italy including 169,370 residents aged 65 years or more.
                Two hundred and seventy-five cases 550 controls were analyzed. Influenza vaccination was effective in preventing 33% of hospitalization due to pneumonia/influenza. The fraction of hospital admissions preventable by extending the vaccination was 17%. When the analysis was limited to self-respondents to the questionnaire (excluding next-of-kin) and to pneumonia/influenza as primary discharge diagnosis, protection from hospitalization by vaccination almost reached 50%, a better result in comparison with most case-control studies.
                Influenza vaccination was shown to be successful in reducing hospital admissions due to pneumonia and influenza. A large number of hospitalizations could be reduced extending the vaccination campaign. The effect of influenza vaccination on the occurrence and severity of influenza virus infection in a population residing in nursing homes was studied through a program by the Osaka Prefectural Government, which is the first and official support for influenza vaccination of the elderly population during an influenza A (H3N2) epidemic in JAPAN:
                A cohort study located in the Osaka Prefecture, Japan, followed the outcomes of elderly nursing home residents who received influenza vaccinations (n = 10,739) in comparison with control subjects who did not receive influenza vaccinations (n = 11,723) and monitored clinically the onset of serious morbidity and mortality of influenza illness. Subjects were 22,462 persons older than 65 years who resided in 301 welfare nursing homes in the Osaka Prefecture, Japan during an influenza A (H3N2) epidemic in 1998 to 1999.
                Of 22,462 individuals living in 301 nursing homes, 10,739 received either one dose (2027 subjects) or two doses (8712 subjects) of inactivated, subunit trivalent influenza vaccine. Through the period from November 1998 to March 1999, there were 950 cases of influenza infection diagnosed clinically with cases by virus isolation and/or serology. There were statistically significantly fewer clinical cases of influenza, hospital admissions due to severe infection, and deaths due to influenza in the vaccinated cohort (256 cases, 32 hospital admissions, and one death) compared with the unvaccinated controls (694 cases, 150 hospital admissions, and five deaths). Vaccination was equally effective in those who received one dose of vaccine as in those who received two doses. No serious adverse reactions to vaccination were recorded. Thus, influenza vaccination is safe and effective in this population and should be an integral part of the routine care of persons aged 65 years and older residing in nursing homes.
                This study provides an analysis of the clinical efficacy of influenza vaccination in a large cohort of nursing home residents in JAPAN: Annual influenza vaccine administration requires the attention of all nursing home attendants, physicians, and public health organizations. nan Upper respiratory tract illnesses have been associated with an increased risk of ischemic heart disease and stroke. During two influenza seasons, we assessed the influence of vaccination against influenza on the risk of hospitalization for heart disease and stroke, hospitalization for pneumonia and influenza, and death from all causes.
                Cohorts of community-dwelling members of three large managed-care organizations who were at least 65 years old were studied during the 1998-1999 and 1999-2000 influenza seasons. Administrative and clinical data were used to evaluate outcomes, with multivariable logistic regression to control for base-line demographic and health characteristics of the subjects.
                There were 140,055 subjects in the 1998-1999 cohort and 146,328 in the 1999-2000 cohort, of which 55.5 percent and 59.7 percent, respectively, were immunized. At base line, vaccinated subjects were on average sicker, having higher rates of most coexisting conditions, outpatient care, and prior hospitalization for pneumonia than unvaccinated subjects. Unvaccinated subjects, however, were more likely to have been given a prior diagnosis of dementia or stroke. Vaccination against influenza was associated with a reduction in the risk of hospitalization for cardiac disease (reduction of 19 percent during both seasons [P<0.001]), cerebrovascular disease (reduction of 16 percent during the 1998-1999 season [P<0.018] and 23 percent during the 1999-2000 season [P<0.001]), and pneumonia or influenza (reduction of 32 percent during the 1998-1999 season [P<0.001] and 29 percent during the 1999-2000 season [P<0.001]) and a reduction in the risk of death from all causes (reduction of 48 percent during the 1998-1999 season [P<0.001] and 50 percent during the 1999-2000 season [P<0.001]). In analyses according to age, the presence or absence of major medical conditions at base line, and study site, the findings were consistent across all subgroups.
                In the elderly, vaccination against influenza is associated with reductions in the risk of hospitalization for heart disease, cerebrovascular disease, and pneumonia or influenza as well as the risk of death from all causes during influenza seasons. These findings highlight the benefits of vaccination and support efforts to increase the rates of vaccination among the elderly.
                Copyright 2003 Massachusetts Medical Society An outbreak of influenza A occurred in an elderly population in a Maryland nursing home between December 8, 1980 and January 13, 1981 and involved 76 of the 170 residents. Throat swabs from two of 10 acutely ill residents yielded influenza A virus similar to the A/Taiwan/1/79 strain. Fourfold or greater increases in the titer of complement-fixing (CF) or hemagglutination-inhibiting (HI) antibodies were detected in paired sera from four of five ill residents and from none of four well residents. One hundred (62.9 per cent) of 159 residents with known vaccination histories had been vaccinated with trivalent influenza virus vaccine in October and November 1980. Crude illness attack rates and mortality rates were similar in vaccinees and nonvaccinees. Various risk factors and hypotheses were examined in an attempt to explain the apparent lack of vaccine efficacy. In a three-year influenza vaccination programme carried out among elderly patients these were found to have a lower haemagglutination-inhibiting antibody level and a poorer serological response to vaccination than younger persons in the same city. Although there was little difference in overall respiratory illness between the vaccinated and unvaccinated groups until the third year of observation, those who received vaccine showed a substantially smaller incidence of bronchopneumonia and a significantly lower mortality than those not so protected. The observations are believed to justify the giving of influenza vaccine in this age-group.
The available evidence is of poor quality and provides no guidance regarding the safety, efficacy or effectiveness of influenza vaccines for people aged 65 years or older. To resolve the uncertainty, an adequately powered publicly-funded randomised, placebo-controlled trial run over several seasons should be undertaken.