Effectiveness of influenza vaccination of day care children in reducing influenza-related morbidity among household contacts. Effect of influenza vaccination of children on infection rates in Hutterite communities: a randomized trial. Protective efficacy against pandemic influenza of seasonal influenza vaccination in children in Hong Kong: a randomized controlled trial. Socioeconomic impact of influenza on healthy children and their families Efficacy of live attenuated and inactivated influenza vaccines in schoolchildren and their unvaccinated contacts in Novgorod, Russia. Herd immunity in adults against influenza-related illnesses with use of the trivalent-live attenuated influenza vaccine (CAIV-T) in children. Effectiveness of influenza vaccination of children with recurrent respiratory tract infections in reducing respiratory-related morbidity within the households. Live attenuated and inactivated influenza vaccine in school-age children. Comparison of heterotypic protection against influenza A/Taiwan/86 (H1N1) by attenuated and inactivated vaccines to A/Chile/83-like viruses.
CONTEXT A growing proportion of young children in the United States participate in day care , and these children are considered to be at high risk for influenza infection . Whether vaccinating day care children reduces household transmission of influenza is not known . OBJECTIVE To evaluate the effect of  vaccinating day care children  on reducing influenza-related morbidity among their household contacts . DESIGN Single-blind , r and omized controlled trial conducted during the 1996 - 1997 influenza season . SETTING Ten day care centers for children of US Navy personnel in San Diego , Calif. PARTICIPANTS A total of 149 day care attendees ( aged 24 - 60 months ) and their families were r and omized ; 127 children and their 328 household contacts received 2 vaccine doses and were included in the analysis . INTERVENTIONS Inactivated influenza vaccine was administered to 60 children with 162 household contacts , and hepatitis A vaccine as a control was administered to 67 age-matched children with 166 household contacts . MAIN OUTCOME MEASURES Information regarding febrile respiratory illnesses and related morbidity for household contacts of influenza-vaccinated vs control children ( subgrouped by influenza-vaccinated and unvaccinated contacts ) , obtained by telephone interviews with parents every 2 weeks from November 1996 through April 1997 . RESULTS Influenza-unvaccinated household contacts ( n = 120 ) of influenza-vaccinated day care children had 42 % fewer febrile respiratory illnesses ( P = .04 ) compared with unvaccinated household contacts of control children . Among school-aged household contacts ( aged 5 - 17 years ) , there was an 80 % reduction among contacts of vaccinated children ( n = 28 ) vs contacts of unvaccinated children ( n = 31 ) in febrile respiratory illnesses ( P = .01 ) , as well as reductions of more than 70 % in school days missed ( P = .02 ) , reported earaches ( P = .02 ) , physician visits ( P = .007 ) , physician-prescribed antibiotics ( P = .02 ) , and adults who missed work to take care of ill children ( P = .04 ) . CONCLUSIONS These results indicate that vaccinating day care children against influenza helps reduce influenza-related morbidity among their household contacts , particularly among school-aged contacts . Future studies should be conducted in civilian population s to assess the full effect of vaccinating day care children against influenza . JAMA . 2000;284:1677 - 1682 CONTEXT Children and adolescents appear to play an important role in the transmission of influenza . Selectively vaccinating youngsters against influenza may interrupt virus transmission and protect those not immunized . OBJECTIVE To assess whether vaccinating children and adolescents with inactivated influenza vaccine could prevent influenza in other community members . DESIGN , SETTING , AND PARTICIPANTS A cluster r and omized trial involving 947 Canadian children and adolescents aged 36 months to 15 years who received study vaccine and 2326 community members who did not receive the study vaccine in 49 Hutterite colonies in Alberta , Saskatchewan , and Manitoba . Follow-up began December 28 , 2008 , and ended June 23 , 2009 . INTERVENTION Children were r and omly assigned according to community and in a blinded manner to receive st and ard dosing of either inactivated trivalent influenza vaccine or hepatitis A vaccine , which was used as a control . MAIN OUTCOME MEASURES Confirmed influenza A and B infection using a real-time reverse transcriptase polymerase chain reaction ( RT-PCR ) assay and by measuring serum hemagglutination inhibition titers . RESULTS The mean rate of study vaccine coverage among eligible participants was 83 % ( range , 53%-100 % ) for the influenza vaccine colonies and 79 % ( range , 50%-100 % ) for the hepatitis A vaccine colonies . Among nonrecipients , 39 of 1271 ( 3.1 % ) in the influenza vaccine colonies and 80 of 1055 ( 7.6 % ) in the hepatitis A vaccine colonies had influenza illness confirmed by RT-PCR , for a protective effectiveness of 61 % ( 95 % confidence interval [ CI ] , 8%-83 % ; P = .03 ) . Among all study participants ( those who were and those who were not vaccinated ) , 80 of 1773 ( 4.5 % ) in the influenza vaccine colonies and 159 of 1500 ( 10.6 % ) in the hepatitis A vaccine colonies had influenza illness confirmed by RT-PCR for an overall protective effectiveness of 59 % ( 95 % CI , 5%-82 % ; P = .04 ) . No serious vaccine adverse events were observed . CONCLUSION Immunizing children and adolescents with inactivated influenza vaccine significantly protected unimmunized residents of rural communities against influenza . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00877396 BACKGROUND The efficacy of seasonal influenza vaccination against 2009 p and emic influenza A(H1N1 ) remains unclear . METHODS One child aged 6 - 17 years in each of 796 households was r and omized to receive 2009 - 2010 seasonal trivalent inactivated influenza vaccine ( TIV ) or saline placebo between August 2009 and February 2010 . Households were followed up with serology , symptom diaries , and collection of respiratory specimens during illnesses . The primary outcomes were influenza infection confirmed by reverse-transcription polymerase chain reaction ( RT-PCR ) or a ≥4-fold rise in serum antibody titer measured by hemagglutination inhibition assay . RESULTS Receipt of TIV led to 8 - 13-fold mean geometric rises in antibody titers against seasonal A and B viruses , but only 1.5-fold mean geometric rises against the p and emic A(H1N1 ) virus that was not included in the vaccine . Children who received TIV had a reduced risk of seasonal influenza B confirmed by RT-PCR , with a vaccine efficacy estimate of 66 % ( 95 % confidence interval [ CI ] , 31%-83 % ) . Children who received TIV also a had reduced risk of p and emic influenza A(H1N1 ) indicated by serology , with a vaccine efficacy estimate of 47 % ( 95 % CI , 15%-67 % ) . CONCLUSIONS Seasonal TIV prevented p and emic influenza A(H1N1 ) and influenza B infections in children . P and emic A(H1N1 ) circulated at the time of vaccination and for a short time afterward with no substantial seasonal influenza activity during that period . The potential mechanism for seasonal TIV to provide protection , possibly short lived , for children against p and emic A(H1N1 ) infection despite poor cross-reactive serologic response deserves further investigation . Clinical Trials Registration . NCT00792051 Background . Recent studies indicate that influenza can be clinical ly important in otherwise healthy children . However , the interpretation of many studies is limited because of lack of laboratory confirmation of influenza-like illnesses . Therefore it is difficult to conclude whether the socioeconomic impact of influenza justifies vaccinating all children regardless of age or underlying chronic disorders . Methods . We prospect ively collected data from 3771 children younger than 14 years of age presenting to emergency departments or primary care pediatricians with symptoms of respiratory tract infection during the influenza season of 2001 to 2002 . Influenza infections were verified by virus culture or polymerase chain reaction . We additionally r and omized 303 children age 6 months to 5 years to receive either influenza vaccine ( n = 202 ) or no vaccination ( n = 101 ) before the influenza season . The socioeconomic impact of influenza was assessed for both the participating children and their household contacts . Results . Influenza was documented in 352 ( 9.3 % ) of the 3771 children . Compared with influenza-negative children , children with influenza had longer duration s of fever and absenteeism from day care or school ( P < 0.0001 ) . Further the numbers of medical visits , missed work or school days and the need for help at home to care for the sick children were higher among the household contacts of influenza-positive children ( P < 0.0001 ) . Influenza vaccination reduced significantly the direct and indirect influenza-related costs in healthy children and their unvaccinated family members . Conclusions . The findings of this study support a wider use of influenza vaccine in healthy children of all ages to reduce the socioeconomic burden of influenza on the community 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 Highest attack rates for influenza occur in children . Immunization of schoolchildren with inactivated influenza vaccine in Michigan and Japan was associated with decreased morbidity and mortality , respectively , in older community contacts . An open-labeled , non-r and omized , community-based trial in children with the cold adapted influenza vaccine , trivalent ( CAIV-T )  was initiated to determine the coverage necessary to reduce spread of influenza in the community . Age-specific baseline rates of medically attended acute respiratory illness ( MAARI ) for Scott and White Health Plan ( SWHP ) members at intervention ( Temple and Belton ) and comparison communities ( Waco , Bryan , and College Station ) were obtained in 1997 - 1998 . During three subsequent vaccination years , 4298 , 5251 and 5150 children received one dose per season of CAIV-T.  Vaccinees represented 20 - 25 % of the age-eligible children .  Age-specific MAARI rates were compared for SWHP members in the intervention and comparison sites during the influenza outbreaks . Baseline age-specific MAARI rates per 100 persons for the influenza season were comparable between the intervention and comparison communities . In the subsequent three influenza seasons , the age groups 35 - 44 , 45 - 54 , 55 - 65 and > 64 years experienced reductions in MAARI rates in the intervention communities . In adults > or = 35 years of age , significant reductions in MAARI of 0.08 ( 95 % CI : 0.04 , 0.13 ) , 0.18 ( 95 % CI : 0.14 , 0.22 ) and 0.15 ( 95 % CI : 0.12 , 0.19 ) , were observed in the influenza seasons for vaccination years 1 , 2 and 3 , respectively . No consistent reduction in MAARI rates was detected in the younger age groups . Vaccination of approximately 20 - 25 % of children , 1.5 - 18 years of age in the intervention communities result ed in an indirect protection of 8 - 18 % against MAARI in adults > or = 35 years of age To evaluate the effectiveness of influenza vaccination in reducing respiratory-related morbidity among children with recurrent respiratory tract infections ( RRTIs ) and their household contacts , 127 children aged 6 months-9 years ( 78 males ; median age , 3.7 years ) with a history of RRTIs ( > /=6 episodes per year if aged > /=3 years ; > /=8 episodes per year if aged <3 years ) were r and omized to receive the intranasal virosomal influenza vaccine ( n=64 with 176 household contacts ) or a control placebo ( n=63 with 173 household contacts ) . During influenza season , the vaccinated children had fewer respiratory infections , febrile respiratory illnesses , prescribed antibiotics and antipyretics , and missed school days than the controls , and similar benefits and a reduction in the loss of parental work were observed among their household contacts . This study shows that the benefits of influenza vaccination extend to children with RRTIs and their family members and encourages to recommend its use in such children 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 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 )
Influenza vaccination programmes are assumed to have a herd effect and protect contacts of vaccinated persons from influenza virus infection .