[The comparative characteristics of the safety, immunogenic activity and prophylactic potency of the adult and children types of live influenza vaccine in schoolchildren aged 7-14 years]. A method for assessing the quality of a randomized control trial. Efficacy of intranasal virosomal influenza vaccine in the prevention of recurrent acute otitis media in children. The efficacy of live attenuated, cold-adapted, trivalent, intranasal influenzavirus vaccine in children. Clinical and epidemiological evaluation of a live, cold-adapted influenza vaccine for 3-14-year-olds. Efficacy of live attenuated and inactivated influenza vaccines in schoolchildren and their unvaccinated contacts in Novgorod, Russia. Evaluation of a neuraminidase-specific influenza A virus vaccine in children: antibody responses and effects on two successive outbreaks of natural infection. Influenza vaccine in healthy preschool children. Field trial with human and equine influenza vaccines in children: protection and antibody titres. Effectiveness of inactivated influenza vaccine in preventing acute otitis media in young children: a randomized controlled trial. Studies of the 1996-1997 inactivated influenza vaccine among children attending day care: immunologic response, protection against infection, and clinical effectiveness. Controlled trial of inactivated influenza vaccine containing the a-Hong Kong strain during an outbreak of influenza due to the a-England-42-72 strain. Live attenuated and inactivated influenza vaccine in school-age children. Use of influenza A virus vaccines in seronegative children: live cold-adapted versus inactivated whole virus. Comparison of live attenuated and inactivated influenza vaccines in schoolchildren in Russia: I. Safety and efficacy in two Moscow schools, 1987/88. Efficacy of inactivated and cold-adapted vaccines against influenza A infection, 1985 to 1990: the pediatric experience Study of live recombinant cold-adapted influenza bivalent vaccine of type A for use in children: an epidemiological control trial. Comparison of heterotypic protection against influenza A/Taiwan/86 (H1N1) by attenuated and inactivated vaccines to A/Chile/83-like viruses. Influenza A vaccine decreases the incidence of otitis media in 6- to 30-month-old children in day care. Efficacy of vaccination with live attenuated, cold-adapted, trivalent, intranasal influenza virus vaccine against a variant (A/Sydney) not contained in the vaccine. Comparison of US inactivated split-virus and Russian live attenuated, cold-adapted trivalent influenza vaccines in Russian schoolchildren.
In Russia for prevention of influenza in children , aged from 3 to 14 years , the children 's live influenza vaccine ( LIV ) , based upon A/Leningrad/134/47/57(H2N2 ) master strain ( LIVI ) is used . The need for double immunization appears to be one out of the faulties of this preparation . The study was aim ed to comparing the safety , immunogenic activity and prevention of influenza by  LIV for adults ( LIVII ) ( A/Leningrad/134/17/57(H2N2 master strain ) and LIVI in children aged from 7 to 17 years under similar administration schedule . The safety , the preventive efficacy , humoral and secretory immunity were studied . In total 2486 persons , including 539 children , twice inoculated with LIVI , 971 persons once inoculated with LIVII , and 840 treated by placebo were obserbed . From the data of the clinical observations during 7 days after immunization both vaccines appeared to be low reactogenic . The LIVII advantages in induction of the humoral and secretory antibodies in comparison with children 's vaccine had been revealed . Both vaccines were highly efficacious , the efficiency of both preparations was more pronounced after serologic correction of the diagnosis . The results obtained permit to recommend the single immunization by the variant of LIV at the base on A/Leningrad/134/17/57/(H2N2 ) master strain for prevention of influenza in school children A system has been constructed to evaluate the design , implementation , and analysis of  r and omized control trials ( RCT ) . The degree of quadruple blinding ( the r and omization process , the physicians and patients as to therapy , and the physicians as to ongoing results ) is considered to be the most important aspect of any trial . The analytic techniques are scored with the same emphasis as is placed on the control of bias in the planning and implementation of the studies . Description of the patient and treatment material s and the measurement of various controls of quality have less weight . An index of quality of a RCT is proposed with its pros and cons . If published papers were to approximate these principles , there would be a marked improvement in the quality of r and omized control trials . Finally , a reasonable st and ard design and conduct of trials will facilitate the interpretation of those with conflicting results and help in making valid combinations of undersized trials To evaluate the efficacy of an intranasal , inactivated , virosomal subunit influenza vaccine for prevention of new episodes of acute otitis media ( AOM ) in children with recurrent AOM , 133 children aged 1 - 5 years were r and omized to receive the vaccine  ( n=67 ) or  no vaccination  ( n=66 ) . During a 6-month period , 24 ( 35.8 % ) vaccine recipients had 32 episodes of AOM ; 42 ( 63.6 % ) control subjects had 64 episodes . The overall efficacy of vaccination in preventing AOM was 43.7 % ( 95 % confidence interval , 18.6 - 61.1 ; P=.002 ) . Children vaccinated before influenza season had a significantly better outcome than did those vaccinated after the onset of influenza season . The cumulative duration of middle ear effusion was significantly less in vaccinated children than in control subjects . Data suggest that the intranasal virosomal influenza vaccine might be considered among the options for the prevention of AOM in children < 5 years old with recurrent AOM BACKGROUND Influenzavirus vaccine is used infrequently in healthy children , even though the rates of influenza in this group are high . We conducted a multicenter , double-blind , placebo-controlled trial of a live attenuated , cold-adapted , trivalent influenzavirus vaccine in children 15 to 71 months old . METHODS Two hundred eighty-eight children were assigned to receive one dose of vaccine or placebo given by intranasal spray , and 1314 were assigned to receive two doses approximately 60 days apart . The strains included in the vaccine were antigenically equivalent to those in the inactivated influenzavirus vaccine in use at the time . The subjects were monitored with viral cultures for influenza during the subsequent influenza season . A case of influenza was defined as an illness associated with the isolation of wild-type influenzavirus from respiratory secretions . RESULTS The intranasal vaccine was accepted and well tolerated . Among children who were initially seronegative , antibody titers increased by a factor of four in 61 to 96 percent , depending on the influenza strain . Culture-positive influenza was significantly less common in the vaccine group ( 14 cases among 1070 subjects ) than the placebo group ( 95 cases among 532 subjects ) . The vaccine efficacy was 93 percent ( 95 percent confidence interval , 88 to 96 percent ) against culture-confirmed influenza . Both the one-dose regimen ( 89 percent efficacy ) and the two-dose regimen ( 94 percent efficacy ) were efficacious , and the vaccine was efficacious against both strains of influenza circulating in 1996 - 1997 , A(H3N2 ) and B. The vaccinated children had significantly fewer febrile illnesses , including 30 percent fewer episodes of febrile otitis media ( 95 percent confidence interval , 18 to 45 percent ; P<0.001 ) . CONCLUSIONS A live attenuated , cold-adapted influenzavirus vaccine was safe , immunogenic , and effective against influenza A(H3N2 ) and B in healthy children Reported is a study of live , cold-adapted ( CA ) reassortant mono- , di- , and trivalent influenza type A and B vaccines in a series of controlled clinical and epidemiological investigations involving nearly 130 000 children aged 3 - 15 years . The results of clinical , immunological , and morbidity investigations of the vaccinees and a control group over 6-months ' follow-up indicated that the vaccines were completely attenuated by the children . Transient febrile reactions occurred in < 1 % of the children after vaccination , including double seronegative individuals with low antibody titres . The type A reisolates examined were genetically stable . The reassortants did not suppress each other after simultaneous inoculation of children and stimulated antibody response to influenza virus strains A1 , A3 , and B. The incidence of influenza-like diseases was approximately 30 - 40 % lower among the vaccinated group than among the control group . The study demonstrates , for the first time , the efficacy of CA vaccine  against infections caused by influenza B virus Children aged 7 - 14 years in Novgorod , Russia , were given Russian live cold-adapted or inactivated influenza vaccines or placebo over a 2-year period . Schools were r and omly assigned as a whole to one of the preparations . In the first year , the vaccines were bivalent , containing types A ( H3N2 ) and A ( H1N1 ) components . In the second year , the vaccines also contained a type B component . In the first year , all viruses isolated were type A ( H3N2 ) ; in the second , about three-quarters of the isolates were type B and the rest type A ( H1N1 ) . During both years , the vaccines protected the vaccinated children . Where significant differences existed , the live attenuated vaccine was more protective than the inactivated . Vaccination rates in schools in which live attenuated vaccines had been used were inversely related to illness rates of staff and unvaccinated children , suggesting that viral transmission had been reduced by the vaccine Three groups of children were immunized with an inactivated Port Chalmers ( H3ChN2Ch ) influenza vaccine ( group A ) , a neuraminidase-specific ( Heq1N2Ch ) influenza vaccine ( group B ) , or a placebo . Immunization induced seroconversion for H3Ch and N2Ch-specific antibody in group A and for N2Ch antibody in group B. The protective efficacies observed against naturally acquired illness with the Port Chalmers strain of influneza A virus were 68.7 % and 37.4 % in groups A and B , respectively , in comparison to the placebo group , and those against illness produced by the subsequent outbreak of the Victoria strain were 80.0 % and 72.7 % . These data support the role of neuraminidase-specific immunization in protection against influenza . Although the degree of protection after vaccination with the Heq1N2Ch vaccine was less than that provided by the biphasic H3ChN2Ch vaccine against the Port Chalmers strain , it appeared to be similar in the two vaccine study groups against the Victoria strain BACKGROUND Studies of  influenza vaccination in healthy children have not definitely answered the question of their efficacy . METHODS We have carried out a r and omized trial in a well selected population of healthy preschool children in Sardinia , Italy . During October 1995 , 344 children aged 1 to 6 years , were r and omly assigned to receive  influenza vaccine  ( n=177 ) or no treatment ( n=167 ) . Two doses of a trivalent subvirion vaccine , containing 15 mg of highly purified surface antigens from the component strains A/Johannesburg/33/94-like , A/Singapore/6/86-like and B/ Beijing/184/ 93-like were administered . Follow-up data were collected from December 1 , 1995 through April 30 , 1996 . RESULTS Seroconversion was documented in 17 out of 17 children . No specific systemic symptoms or severe local reactions were observed after vaccination . Influenza-like episodes , defined by the presence of fever and cough or sore throat that lasted at least 72 hours , occurred in 63 ( 37.7 % ) of unvaccinated children and in 22 ( 12.4 % ) of vaccinated ones . The corresponding reduction in disease incidence was 67 % ( 95 % CI : 0.59 - 0.74 ) . Three episodes of otitis were observed among children in the control group versus zero among vaccinated children ( p=0.07 ) . Mean duration of day care center absenteism was significantly reduced by vaccination ( 2.3 days in unvaccinated and 0.5 day in vaccinated children , p<0.001 ) CONCLUSIONS Influenza vaccine is safe and effective in healthy preschool children . However the favourable implication s of vaccination on disease rate in subsequent years have to be evaluated A placebo-controlled influenza vaccination trial was carried out on 374 children in the winter of 1967 - 68 . The children were r and omly vaccinated with 300 CCA of A2/Engl and /1/1966 , 300 CCA of A/equine 2/Miami/1963 , or with a placebo . During this winter an influenza outbreak occurred , caused by A2/Nederl and /1968 . The A2 vaccine yielded a protection rate of 58 % ( P = 0.02 ) and the A/equine 2 vaccine a rate of 19 % ( P = 0.33 ) . Serological data revealed that all influenza infections occurred in subjects who had a pre-epidemic  haemagglutination inhibition titre  below 150 . The antibody response against various human influenza A2 viruses and against the horse strain ( A/equine 2 ) is discussed CONTEXT Acute otitis media ( AOM ) frequently complicates influenza infection . Previous studies have found influenza vaccine effective in reducing the occurrence of AOM in children mainly older than 2 years . OBJECTIVE To evaluate the effectiveness of inactivated influenza vaccine in preventing AOM in children aged 6 to 24 months . DESIGN , SETTING , AND PATIENTS R and omized , double-blind , placebo-controlled trial of 786 children aged 6 to 24 months enrolled at Children 's Hospital of Pittsburgh before the 1999 - 2000 ( 411 children ) and 2000 - 2001 ( 375 children ) respiratory seasons ( defined as December 1 through March 31 of the respective following year ) . Children received influenza vaccine or placebo in a 2:1 ratio . The first cohort was observed for 1 year and the second cohort until the end of the ensuing respiratory season . INTERVENTION Two doses ( 0.25 mL each ) of inactivated trivalent subvirion influenza vaccine or placebo were administered intramuscularly approximately 4 weeks apart . MAIN OUTCOME MEASURES Proportion of children who developed AOM , monthly occurrence rate of AOM , estimated proportion of time with middle ear effusion , and utilization of selected health care and related re sources . RESULTS Of the 66 children in the vaccine group from whom serum sample s were collected , seroconversion against strains in the vaccine formulations developed in 88.6 % to 96.8 % , depending on the specific strain . The efficacy of the vaccine against culture-confirmed influenza was 66 % ( 95 % confidence interval [ CI ] , 34%-82 % ) in 1999 - 2000 and -7 % ( 95 % CI , -247 % to 67 % ) in 2000 - 2001 ; however , influenza attack rates differed between these 2 periods ( in the placebo group , 15.9 % and 3.3 % , respectively ) . Compared with placebo , influenza vaccine did not reduce the proportion of children who had at least 1 episode of AOM during the respiratory season ( in the first cohort : vaccine , 49.2 % vs placebo , 52.2 % ; P = .56 ] ; in the second cohort : vaccine , 55.8 % vs placebo , 48.3 % ; P = .17 ) . The vaccine also did not reduce the monthly rate of AOM ; the estimated proportion of time with middle ear effusion ; or the utilization of selected health care and related re sources . There were also no differences between the vaccine and placebo groups regarding any of these outcomes during peak influenza periods . The vaccines administered to both cohorts of children were well tolerated . CONCLUSION Administration of inactivated trivalent influenza vaccine to children aged 6 to 24 months did not reduce their burden of AOM or their utilization of selected health care and related re sources A r and omized , blinded , pilot study of influenza vaccine administered to children attending day care centers was conducted during the 1996 - 1997 winter . Vaccine efficacy in preventing serologically proven influenza virus infection was 0.45 ( 95 % confidence limit [ CL ] : -0.02 , 0.69 ) for influenza B and 0.31 ( 95 % CL : -0.95 , 0.73 ) for influenza A(H3N2 ) . For both influenza A(H3N2 ) and B , children without preexisting hemagglutination inhibition ( HI ) antibody to these antigens had lower antibody responses to vaccine , were less likely to develop a serological response , and were more likely to develop serological evidence of influenza infection . Although there were no reductions in respiratory or febrile respiratory illnesses among all vaccinated children , there was a trend for reductions in such illnesses among vaccinated children with preexisting HI antibodies to influenza A(H3N2 ) and B. Therefore , immunologic priming in young children may be important for vaccine response and for protection against infection . Larger studies are needed in other influenza seasons to assess vaccine efficacy and clinical effectiveness Abstract A trial of inactivated influenza vaccine containing the A/Hong Kong/68 strain was made in 800 boys in a boarding-school starting in 1970 . The boys had serum sample s withdrawn for antibody estimations and were allocated at r and om to vaccine and control groups . During an outbreak of influenza A due to the A/Engl and /42/72 strain , all boys with clinical influenza reported to the medical officer and the diagnosis was confirmed by laboratory examination . The vaccine was shown to confer substantial protection against the new virus strain . The presence of haemagglutinating ( H.I. ) antibody to either strain 6 weeks before the outbreak was associated with protection against influenza . In boys with H.I. antibody to A/Hong Kong/68 virus the attack-rate was 6 % , compared with 25 % in boys with no H.I. antibody to either virus strain . No influenza occurred in boys known to have H.I. antibody to the A/Engl and /42/72 strain . Three-quarters of the boys in whom A/Hong Kong/68 H.I. antibody had been naturally acquired developed A/Engl and / 42/72 H.I. antibody after vaccination . In contrast , the development of A/Engl and /42/72 H.I. antibody was less frequent after revaccination of boys in whom the A/Hong Kong/68 H.I. antibody had been induced by vaccination . A vaccine prepared from the A/Hong Kong/68 strain conferred substantial protection despite the recent antigenic shift of the influenza virus In 1985 , we enrolled 189 school-age children by family in a double-blind study to determine protection against influenza by a single dose of cold-recombinant bivalent A vaccine or commercial trivalent inactivated vaccine compared with placebo .  All children in school or day care , 3 to 18 years of age , in an enrolled family received the same preparation . Following vaccination , 60 % and 21 % of cold-recombinant bivalent A vaccine recipients and 73 % and 83 % of trivalent inactivated vaccine recipients demonstrated fourfold or greater response in hemagglutination-inhibition antibody titer to A/H1N1 and A/H3N2 , respectively . Sixty-seven percent of all trivalent inactivated vaccine recipients demonstrated a fourfold or greater serologic response to H1N1 , H3N2 , and influenza B following a single dose of vaccine . During the 1985 - 1986 influenza B/Ann Arbor epidemic , heterotypic protection afforded by the influenza B/USSR component of trivalent inactivated vaccine was 62 % compared with placebo . A single dose of trivalent inactivated vaccine protected school-age children , 6 to 19 years of age , from influenza B infection ; the rate of protection was 64 % against infection and 73 % against febrile illness We report the safety and antigenicity of influenza A vaccines  in seronegative children one to seven years of age . A natural H1N1 challenge that occurred shortly after completion of the vaccination program permitted an evaluation of efficacy . Twenty-eight subjects were inoculated with live cold-adapted ( ca ) influenza A/Washington/897/80 ( H3N2 ) , 29 with ca influenza A/California/10/78 ( H1N1 ) , 24 with inactivated whole-virus influenza A/Bangkok/79 ( H3N2 ) , and 30 with a placebo . The ca vaccines were well tolerated , whereas the inactivated vaccine caused adverse reactions in about one-third of the children . Fifty-seven percent of the ca H1N1 recipients showed serological responses , contrasted with 84 % and 100 % of subjects receiving the ca or inactivated H3N2 vaccines , respectively . None of the 16 children with induced H1N1 antibody developed clinical ly apparent influenza-like illness , compared with eleven of the 51 initially seronegative children who did not receive the ca H1N1 vaccine and with four of the 12 who failed to respond . Results of the efficacy field trial suggest protection against infection and symptomatic illness in children inoculated with ca H1N1 , despite its failure to stimulate high levels of hemagglutinin-inhibiting antibody The performance of two doses of cold-adapted live attenuated vaccine versus one dose of whole-virus inactivated vaccine was compared in 8 - 15-year-old schoolchildren in two schools in Moscow , Russia , during the winter of 1987/88 . Both vaccines gave rise to low frequencies of associated febrile or systemic reactions , but the inactivated vaccine , delivered by jet injector , did cause small local reactions in about half of the children . Immunogenicity was higher for both vaccines in antibody-free children , and higher levels of serum antibody were detected following use of inactivated vaccine . During the winter , influenza A ( H3N2 ) and influenza B viruses circulated in Moscow . A clear outbreak of ( H3N2 ) virus occurred in both schools , and infections with type B virus also occurred in one school . The influenza A/Philippines/2/82 ( H3N2 ) component of both vaccines exhibited protective efficacy of about 40 % ( p < 0.05 ) against serologically proven infection caused by the antigenically drifted A/Sichuan/2/87 (H3N2)-like epidemic viruses in one school . In another school where illnesses associated with antibody rise were documented , efficacy was seen for both vaccines in reduction of illnesses , and of illnesses with serological evidence of infection , but statistical significance was not achieved Background . Influenza is a common and potentially serious infection in children . Although there is interest in broadening the use of influenza vaccine in healthy children , there are few large , r and omized , controlled trials that evaluate the safety and efficacy of inactivated vaccine in the pediatric population . Methods . From 1985 through 1990 a r and omized , controlled trial of cold-adapted and inactivated vaccines for the prevention of influenza A disease was conducted at V and erbilt University , and the cumulative results from this trial in patients of all ages have been previously published . We reanalyzed the data from this trial in the subset of patients who were younger than 16 years at the time of their participation . We determined vaccine safety , immunogenicity and efficacy , based on culture-positive illness and seroconversion , in this subset of patients . Results . During the 5 years of the study , 791 children younger than 16 years received 1809 doses of either inactivated or cold-adapted vaccine or placebo . The vaccines were well-tolerated , and there were no serious reactions . Inactivated trivalent influenza vaccines were 91.4 and 77.3 % efficacious in preventing symptomatic , culture-positive influenza A H1N1 and H3N2 illness , respectively . The efficacy of the inactivated vaccine based on hemagglutination inhibition assay seroconversion was 67.1 and 65.5 % , respectively , for H1N1 and H3N2 serotypes . Conclusions . Inactivated trivalent influenza A vaccines are well-tolerated and efficacious in the prevention of influenza A disease in children 1 to 16 years old Live cold-adapted recombinant bivalent vaccine of influenza type A was studied in a controlled field trial in 1982 - 1983 among nearly 30,000 children 3 - 15 years old . The bivalent vaccine consisted of recombinants 47/25/1 ( H1N1 ) and 47/7/2 ( H3N2 ) of wild-type viruses A/Brazil/11/78 ( H1N1 ) and A/Bangkok/1/79 ( H3N2 ) with cold-adapted donor A/Leningrad/134/47/57 ( H2N2 ) . The recombinants which received mutant nonglycoprotein genes from cold-adapted donor did not suppress each other after simultaneous inoculation of children and stimulated antibody response to both strains . The bivalent vaccine was completely attenuated for children . It caused less than 1 % transient febrile reactions during five days after the first vaccination , including double seronegative individuals with low antibody titres to both vaccinal strains . The cold-adapted bivalent vaccine tested proved to be safe for children according to the analysis of morbidity studies among vaccines and a control group performed during the five days and the following six months after the first immunization . There is a similar distribution of non-influenza illnesses and a statistically significant decrease in influenza-like diseases among vaccines compared to the control group . In the four months after the immunization programme was completed , epidemics of influenza A H1N1 and H3N2 occurred . The incidence of influenza-like diseases was approximately 50 % less in the vaccinated than in the control groups . This is the first evidence of safety and protective efficacy of recombinant live influenza vaccine for children 3 - 15 years of age Children ( n = 192 ) aged 3 - 19 years from 98 families completed this double-blind , placebo-controlled study comparing the efficacy of a bivalent attenuated ( CR ) vaccine with trivalent inactivated ( TI ) vaccine . Both vaccines contained A/Chile/83 (H1N1)-like antigens . After vaccination the geometric mean titer to A/Taiwan/86 ( H1N1 ) was 1:36 in the CR group , 1:92 in the TI group , and 1:5 in the placebo group . During the influenza A/Taiwan/86 ( H1N1 ) epidemic , 21.4 % of CR recipients , 16.7 % of TI recipients , and 43.9 % of placebo recipients were infected with influenza A/Taiwan . TI vaccine provided better heterotypic protection than did CR vaccine for children aged 10 - 18 years ( infection rate , 0 vs. 24 % , respectively ; P less than .025 ) ; in contrast , in the younger children ( 3 - 9 years ) , CR vaccine tended to be more protective ( 19 % vs. 26 % for TI ) OBJECTIVE To determine if the use of influenza vaccine in children in day care decreases the incidence of otitis media during the influenza season . DESIGN Prospect i ve cohort study . SETTING Eight day-care centers in North Carolina . PARTICIPANTS One hundred eighty-six children aged 6 to 30 months . INTERVENTION Half the participants received trivalent subvirion influenza virus vaccine . MEASUREMENTS Acute otitis media ( AOM ) and serous otitis media ( SOM ) were assessed biweekly from mid-November 1993 to mid-March 1994 by visual and tympanometric examinations performed by " blinded " observers . The winter season was divided into three periods-before , during , and after influenza season-- and the number of children with AOM or SOM during each period was determined . Unadjusted and adjusted odds ratios ( ORs ) were computed , while controlling for race and sex using logistic regression methods . RESULTS Influenza vaccine was protective against AOM ( OR = 0.69 , 95 % CI , 0.49 - 0.98 ) during the influenza season . Although there may have been some protection against SOM ( OR = 0.75 , 95 % CI , 0.54 - 1.02 ) statistical significance was not achieved . Myringotomy tubes were also significantly protective against AOM and SOM during all three time periods , with ORs between 0.34 and 0.52 , but the greatest protection was seen during the influenza period . CONCLUSIONS Influenza vaccination of 6- to 30-month-old children in day care was associated with a decreased incidence of otitis media during the influenza season . Myringotomy tubes protected against AOM and SOM during all 16 weeks monitored OBJECTIVE To determine the safety , immunogenicity , and efficacy of revaccination of children with live attenuated influenza vaccine .  STUDY DESIGN A 2-year multicenter , double-blind , placebo-controlled , efficacy field trial of live attenuated , cold-adapted trivalent influenza vaccine administered by nasal spray to children . This report summarizes year 2 results , a year in which the epidemic strain of influenza A/Sydney was not well matched to the vaccine strains . Each year , vaccine strains were antigenically equivalent to the contemporary inactivated influenza vaccine . In year 2 , a single intranasal revaccination was administered . Active surveillance for influenza was conducted during the influenza season by means of viral cultures . Influenza cases were defined as illnesses with wild-type influenza virus isolated from respiratory secretions . RESULTS In year 2 , 1358 ( 85 % ) children , 26 to 85 months of age , returned for revaccination . The intranasal vaccine was easily accepted , well tolerated , and immunogenic . Revaccination result ed in 82 % to 100 % of the vaccinated children in a subset studied for immunogenicity being seropositive as compared with 26 % to 65 % of placebo recipients , depending on the influenza strain tested . No serious adverse events were associated with the vaccine . In addition to the strains in the vaccine , antibody was induced to the variant strain A/Sydney/H3N2 . In year 2 , influenza A/Sydney/H3N2 , a variant not contained in the vaccine , caused 66 of 70 cases of influenza A ; nonetheless , intranasal vaccine was 86 % efficacious in preventing A/Sydney influenza . Eight cases of lower respiratory tract disease were associated with A/Sydney influenza ; all cases were in the placebo group . CONCLUSIONS This live attenuated , cold-adapted influenza vaccine was safe , immunogenic , and efficacious against influenza A/H3N2 ( including a variant , A/Sydney , not contained in the vaccine ) and influenza B. The characteristics of this vaccine make it suitable for routine use in children to prevent influenza In a blinded , placebo-controlled study , the reactogenicity , immunogenicity , and clinical efficacy of single doses of US inactivated split-virus and Russian live attenuated , cold-adapted influenza vaccines were compared in 555 schoolchildren in Vologda , Russia . Serial serum sample s were collected and school absenteeism was assessed . Systemic reactions were rare , but local reactions ( primarily erythema at the injection site ) were observed in 27 % of the inactivated vaccine group , and coryza ( 12 % ) and sore throat ( 8 % ) were observed in the attenuated vaccine group . At 4 weeks after vaccination a > or = 4-fold rise in titer of hemagglutination inhibition antibody to A ( H1N1 ) , A ( H3N2 ) , and B was noted , respectively , among 78 % , 88 % , and 53 % of children who received inactivated vaccine and among 55 % , 79 % , and 30 % of children who received attenuated vaccine . The vaccine efficacy for preventing school absenteeism due to respiratory illness during the period of peak influenza activity was 56 % for inactivated vaccine and 47 % for attenuated vaccine
BACKGROUND Two systematic review s evaluating influenza vaccine efficacy in healthy children have recently been published .