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, randomized controlled trial conducted during the 1996-1997
Setting Ten day care centers for children of US Navy personnel in San Diego,
Participants A total of 149 day care attendees (aged 24-60 months) and their families
were randomized; 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
populations to assess the full effect of vaccinating day care children against