Effectiveness of influenza vaccine in health care professionals: a randomized trial. Do hospital employees benefit from the influenza vaccine? Diagnosis of influenza in the community: relationship of clinical diagnosis to confirmed virological, serologic, or molecular detection of influenza. Randomized, placebo-controlled double blind study on the efficacy of influenza immunization on absenteeism of health care workers. The efficacy of influenza vaccination in healthcare workers in a tropical setting: a prospective investigator blinded observational study. Influenza Vaccination of Healthcare Workers: Critical Analysis of the Evidence for Patient Benefit Underpinning Policies of Enforcement Effects of Repeated Annual Inactivated Influenza Vaccination among Healthcare Personnel on Serum Hemagglutinin Inhibition Antibody Response to A/Perth/16/2009 (H3N2)-like virus during 2010-11. Negative impact of prior influenza vaccination on current influenza vaccination among people infected and not infected in prior season: A test-negative case-control study in Japan. The effect of giving influenza vaccination to general practitioners: a controlled trial [NCT00221676].
CONTEXT Data are limited and conflicting regarding the effectiveness of influenza vaccine in health care professionals . OBJECTIVE To determine the effectiveness of trivalent influenza vaccine in reducing infection , illness , and absence from work in young , healthy health care professionals . DESIGN R and omized , prospect i ve , double-blind , controlled trial over 3 consecutive years , from 1992 - 1993 to 1994 - 1995 . SETTING Two large teaching hospitals in Baltimore , Md. PARTICIPANTS Two hundred sixty-four hospital-based health care professionals without chronic medical problems were recruited ; 49 participated for 2 seasons ; 24 participated for 3 seasons . The mean age was 28.4 years , 75 % were resident physicians , and 57 % were women . INTERVENTION Participants were r and omly assigned to receive either an influenza vaccine or a control ( meningococcal vaccine , pneumococcal vaccine , or placebo ) . Serum sample s for antibody assays were collected at the time of vaccination , 1 month after vaccination , and at the end of the influenza season . Active weekly surveillance for illness was conducted during each influenza epidemic period . MAIN OUTCOME MEASURES Serologically defined influenza infection ( 4-fold increase in hemagglutination-inhibiting antibodies ) , days of febrile respiratory illness , and days absent from work . RESULTS We conducted 359 person-winters of serologic surveillance ( 99.4 % follow-up ) and 4746 person-weeks of illness surveillance ( 100 % follow-up ) . Twenty-four(13.4 % ) of 179 control subjects and 3 ( 1.7 % ) of 180 influenza vaccine recipients had serologic evidence of influenza type A or B infection during the study period . Vaccine efficacy against serologically defined infection was 88 % for influenza A ( 95 % confidence interval [ CI ] , 47%-97 % ; P=.001 ) and 89 % for influenza B ( 95 % CI , 14%-99 % ; P=.03 ) . Among influenza vaccinees , cumulative days of reported febrile respiratory illness were 28.7 per 100 subjects compared with 40.6 per 100 subjects in controls ( P=.57 ) and days of absence were 9.9 per 100 subjects vs 21.1 per 100 subjects in controls ( P=.41 ) . CONCLUSIONS Influenza vaccine is effective in preventing infection by influenza A and B in health care professionals and may reduce reported days of work absence and febrile respiratory illness . These data support a policy of annual influenza vaccination of health care professionals Although current guidelines target hospital employees who contact high-risk patients as a high priority for influenza immunization , there are few data to support or refute this recommendation . Therefore , the authors enrolled 179 hospital employees in a r and omized double-blind  placebo-controlled  clinical trial during the 1985–1986 influenza season .  Influenza immunization was performed without serious adverse reactions and there was no increase in absenteeism attributable to the vaccination . Among those who developed clinical influenza , there was a trend toward fewer days of illness in the vaccinated group compared with the placebo group ( 6.0 vs. 8.0 , p=0.07 ) . There were no statistically significant differences between subjects receiving influenza vaccine and those receiving the placebo when comparing incidences of influenza-like illness , severities of illness , and sick absenteeism .  Influenza immunization of hospital employees was performed at minimal cost and risk but provided little benefit , most likely because of an unexpected drift of the prevalent influenza strain away from the vaccine type BACKGROUND Successful treatment of influenza depends on an accurate diagnosis of the illness and prompt intervention . However , there is a lack of data comparing clinical diagnosis vs laboratory diagnostic techniques . OBJECTIVE To compare the clinical diagnosis of community cases of influenza with various laboratory diagnostic techniques including multiplex , reverse transcription polymerase chain reaction . METHODS Clinical diagnosis , viral isolation , hemagglutinin inhibition serology , and multiplex , reverse transcription polymerase chain reaction were used to diagnose influenza in patients enrolled in international phase 3 studies design ed to investigate the efficacy and safety of an anti-influenza drug ( inhaled zanamivir ) .  Patients clinical ly diagnosed with influenza were enrolled at centers across North America and Europe . RESULTS A total of 791 ( 77 % ) of 1033 patients with laboratory results from all 3 methods were confirmed positive for influenza by 1 or more test results . For 692 patients ( 67 % ) , the results of all 3 tests agreed . Total symptom scores at baseline showed a significant association toward greater severity of symptoms with an increasing number of positive test results ( P<.001 ) . An increasing number of positive test results also showed a significant correlation with a longer time to alleviation of symptoms of influenza in the placebo group ( P = .001 ) . CONCLUSIONS During a time when influenza was known to be circulating and clinical diagnostic criteria were applied , diagnosis of influenza in these trials was accurate in approximately 77 % of adults on clinical grounds alone . This highlights the need for primary care physicians to be alerted to circulating influenza and to be aware that presentation with cough and fever provide the most predictive symptoms BACKGROUND In healthy adults  influenza immunization reduces absenteeism caused by respiratory infections , but data on its efficacy among health care workers are scarce . OBJECTIVE To determine the effect of the conventional inactivated influenza A vaccine on reducing absenteeism related to respiratory infections among pediatric health care providers . STUDY DESIGN A r and omized , placebo-controlled , double blind study on vaccine efficacy was conducted in two pediatric hospitals during the winter season 1996 to 1997 . The primary endpoint was days of work lost from the hospital because of respiratory infections . The documentation of absenteeism was based on personal sickness logs . RESULTS Of the 547 r and omized vaccinees 427 ( 78 % ) persons completed the 4-month follow-up and returned the sickness logs . Immunization failed to reduce episodes of respiratory infections ( 1.8 episodes/ study period among vaccinees vs. 2.0 among controls ) . Similarly the vaccine failed to affect the total number of days the vaccinees suffered from respiratory infections ( 13.5 days vs. 14.6 days , respectively ) . However , days of work lost because of respiratory infections ( 1.0 days vs. 1.4 days , respectively , P = 0.02 ) and especially total numbers of days the study persons felt themselves unable to work when either on or off duty ( 2.5 days vs. 3.5 days , P 0.02 ) were significantly decreased . CONCLUSION Influenza vaccination reduced absenteeism related to respiratory infections by 28 % . We therefore believe that routine annual influenza immunizations should be recommended to health care providers working in pediatric setting INTRODUCTION Influenza vaccine has been shown to be highly effective in temperate regions with well-defined seasonal influenza . Healthcare workers ( HCWs ) are advised to receive regular influenza vaccination to protect themselves and their patients . However , there are limited data on the efficacy of influenza vaccine in HCWs in the tropics . MATERIAL S AND METHODS In this observational , investigator blinded cohort study , bi-monthly question naires recording influenza-like illness ( ILI ) episodes and medical leave were administered to 541 HCWs at the Singapore National University Hospital and KK Women 's and Children 's Hospital from 2004 to 2005 .  ILI was defined according to a st and ard symptom score . RESULTS Baseline characteristics were comparable in both the vaccinated and non-vaccinated groups . Overall , the relative risk of self-reported ILI in vaccinated HCWs was 1.13 [ 95 % confidence interval ( CI ) , 0.98 - 1.13 ; P=0.107 ] ; medical leave taken was lower in the vaccinated group [ mean 0.26+/-0.6 days per visit , compared with 0.30+/-0.5 days in the non-vaccinated group ( P=0.40 ) ] . Because of the reported Northern Hemisphere 2003/04 vaccine mismatch , we stratified the cohort and determined that the group which received a matched vaccine had a relative risk of ILI of 0.49 ( 95 % CI , 0.37 - 0.66 ; P<0.001 ) , achieving a vaccine efficacy of 51 % . Mean medical leave decreased significantly in HCWs who received the matched vaccine , compared with those who did not receive vaccination ( 0.13+/-0.3 vs 0.30+/-0.5 ; P<0.001 ) and with HCWs vaccinated with mismatched strains ( 0.13+/-0.3 vs 0.39+/-0.9 ; P=0.01 ) . CONCLUSIONS A well-matched influenza vaccine is effective in preventing ILI and reducing sickness absence in healthcare workers in tropical setting s. Efforts need to be made to increase influenza vaccination rates and to improve the currently available vaccines Background Four cluster r and omized controlled trials ( c RCTs ) conducted in long-term care facilities ( LTCFs ) have reported reductions in patient risk through increased healthcare worker ( HCW ) influenza vaccination . This evidence has led to expansive policies of enforcement that include all staff of acute care hospitals and other healthcare setting s beyond LTCFs . We critique and quantify the c RCT evidence for indirect patient benefit underpinning policies of m and atory HCW influenza vaccination . Methods Plausibility of the four c RCT findings attributing indirect patient benefits to HCW influenza vaccination was assessed by comparing percentage reductions in patient risk reported by the c RCTs to predicted values . Plausibly predicted values were derived according to the basic mathematical principle of dilution , taking into account HCW influenza vaccine coverage and the specificity of patient outcomes for influenza . Accordingly , predicted values were calculated as a function of relevant compound probabilities including vaccine efficacy ( ranging 40–60 % in HCWs and favourably assuming the same indirect protection conferred through them to patients ) × change in proportionate HCW influenza vaccine coverage ( as reported by each c RCT ) × percentage of a given patient outcome ( e.g. influenza-like illness ( ILI ) or all-cause mortality ) plausibly due to influenza virus . The number needed to vaccinate ( NNV ) for HCWs to indirectly prevent patient death was recalibrated based on real patient data of hospital-acquired influenza , with adjustment for potential under-detection ( 5.2-fold ) , and using favourable assumptions of HCW-attributable risk ( ranging 60–80 % ) . Results In attributing patient benefit to increased HCW influenza vaccine coverage , each c RCT was found to violate the basic mathematical principle of dilution by reporting greater percentage reductions with less influenza-specific patient outcomes ( i.e. , all-cause mortality > ILI > laboratory-confirmed influenza ) and /or patient mortality reductions exceeding even favourably-derived predicted values by at least 6- to 15-fold . If extrapolated to all LTCF and hospital staff in the United States , the prior c RCT -cl aim ed NNV of 8 would implausibly mean > 200,000 and > 675,000 patient deaths , respectively , could be prevented annually by HCW influenza vaccination , inconceivably exceeding total US population mortality estimates due to seasonal influenza each year , or during the 1918 p and emic , respectively . More realistic recalibration based on actual patient data instead shows that at least 6000 to 32,000 hospital workers would need to be vaccinated before a single patient death could potentially be averted . Conclusions The four c RCTs underpinning policies of enforced HCW influenza vaccination attribute implausibly large reductions in patient risk to HCW vaccination , casting serious doubts on their validity . The impression that unvaccinated HCWs place their patients at great influenza peril is exaggerated . Instead , the HCW-attributable risk and vaccine-preventable fraction both remain unknown and the NNV to achieve patient benefit still requires better underst and ing . Although current scientific data are inadequate to support the ethical implementation of enforced HCW influenza vaccination , they do not refute approaches to support voluntary vaccination or other more broadly protective practice s , such as staying home or masking when acutely ill BACKGROUND Recently , lower estimates of influenza vaccine effectiveness ( VE ) against A(H3N2 ) virus illness among those vaccinated during the previous season or multiple seasons have been reported ; however , it is unclear whether these effects are due to differences in immunogenicity . METHODS We performed hemagglutination inhibition antibody ( HI ) assays on serum collected at preseason , ∼ 30 days post-vaccination , and postseason from a prospect i ve cohort of healthcare personnel ( HCP ) . Eligible participants had medical and vaccination records for at least four years ( since July , 2006 ) , including 578 HCP who received 2010 - 11 trivalent inactivated influenza vaccine [ IIV3 , containing A/Perth/16/2009-like A(H3N2 ) ] and 209 HCP who declined vaccination . Estimates of the percentage with high titers ( ≥ 40 and > 100 ) and geometric mean fold change ratios ( GMRs ) to A/Perth/16/2009-like virus by number of prior vaccinations were adjusted for age , sex , race , education , household size , hospital care responsibilities , and study site . RESULTS Post-vaccination GMRs were inversely associated with the number of prior vaccinations , increasing from 2.3 among those with 4 prior vaccinations to 6.2 among HCP with zero prior vaccinations ( F[4,567]=9.97 , p<.0005 ) . Thirty-two percent of HCP with 1 prior vaccination achieved titers > 100 compared to only 11 % of HCP with 4 prior vaccinations ( adjusted odds ratio=6.8 , 95 % CI=3.1 - 15.3 ) . CONCLUSION Our findings point to an exposure-response association between repeated IIV3 vaccination and HI for A(H3N2 ) and are consistent with recent VE observations . Ultimately , better vaccines and vaccine strategies may be needed in order to optimize immunogenicity and VE for HCP and other repeated vaccinees BACKGROUND Accumulating evidence s indicate that repeated influenza vaccination has negative impact on the vaccine effectiveness ( VE ) . However no published studies considered past influenza infection when assessing the VE of repeated vaccination . METHODS Prospect i ve surveillance was conducted from 2009 to 2012 at a community hospital on a small isl and in Japan . The study included all out patients with an influenza-like illness ( ILI ) who attended the hospital , and a rapid diagnostic test ( RDT ) was used to diagnose influenza A/B infection . The VE of trivalent inactivated influenza vaccine ( TIV ) against medically attended influenza A ( MA-fluA ) was estimated using a test-negative case-control study design . The influence of TIV in the prior season on VE in the current season was investigated in the context of MA-fluA during the prior season . RESULTS During the three influenza seasons , 5838 ILI episodes ( 4127 subjects ) were analysed . Subjects who had an episode of MA-fluA in the prior season were at a significantly lower risk of MA-fluA in the current season ( adjusted odds ratio : 0.38 , 95 % CI : 0.30 - 0.50 ) . The overall adjusted VE was 28 % ( 95 % CI , 14 - 40 ) . VE was substantially lower in subjects vaccinated in the prior season compared to those who had not been vaccinated in prior season ( 19 % ; 95 % CI : 0 - 35 vs 46 % ; 95 % CI : 26 - 60 , test for interaction , P value < 0.05 ) . In subjects who did not have MA-fluA in the prior season showed the attenuation of VE due to repeated vaccination ( 13 % ; 95 % CI : -7 to 30 vs 44 % ; 95 % CI : 24 - 59 , test for interaction , P<0.05 ) . However this effect was not detected in subjects who had contracted MA-fluA in the prior season . CONCLUSIONS Negative effects of repeated vaccination were significant among those without history of MA-fluA in the prior season BACKGROUND No efficacy studies of influenza vaccination given to GPs have yet been published . Therefore , our purpose was to assess the effect of an inactivated influenza vaccine given to GPs on the rate of clinical respiratory tract infections ( RTIs ) and proven influenza cases ( influenza positive nose and throat swabs and a 4-fold titre rise ) , while adjusting for important covariates . METHODS In a controlled trial during two consecutive winter periods ( 2002 - 2003 and 2003 - 2004 ) we compared ( 77 and 100 ) vaccinated with ( 45 and 40 ) unvaccinated GPs working in Fl and ers , Belgium .  Influenza antibodies were measured immediately prior to and 3 - 5 weeks after vaccination , as well as after the influenza epidemic . During the influenza epidemic , GPs had to record their contact with influenza cases and their own RTI symptoms every day . If they became ill , the GPs had to take nose and throat swabs during the first 4 days . We performed a multivariate regression analysis for covariates using Generalized Estimating Equations . RESULTS One half of the GPs ( vaccinated or not ) developed an RTI during the 2 influenza epidemics . During the two influenza periods , 8.6 % of the vaccinated and 14.7 % of the unvaccinated GPs had positive swabs for influenza ( RR : 0.59 ; 95%CI : 0.28 - 1.24 ) . Multivariate analysis revealed that influenza vaccination  prevented RTIs and swab-positive influenza only among young GPs ( ORadj : 0.35 ; 95%CI : 0.13 - 0.96 and 0.1 ; 0.01 - 0.75 respectively for 30-year-old GPs ) . Independent of vaccination , a low basic antibody titre against influenza ( ORadj 0.57 ; 95%CI : 0.37 - 0.89 ) and the presence of influenza cases in the family ( ORadj 9.24 ; 95%CI : 2.91 - 29 ) were highly predictive of an episode of swab-positive influenza . CONCLUSION Influenza vaccination was shown to protect against proven influenza among young GPs . GPs , vaccinated or not , who are very vulnerable to influenza are those who have a low basic immunity against influenza and , in particular , those who have family members who develop influenza
BACKGROUND Influenza vaccination is a commonly used intervention to prevent influenza infection in healthcare workers ( HCWs ) and onward transmission to other staff and patients .
We undertook a systematic review to synthesize the latest evidence of the direct epidemiological and economic effectiveness of seasonal influenza vaccination among HCW .