Effectiveness of school-based influenza vaccination.

BACKGROUND Vaccination of children in school is one strategy to reduce the spread of influenza in households and communities. METHODS We identified 11 demographically similar clusters of elementary schools in four states, consisting of one school we assigned to participate in a vaccination program (intervention school) and one or two schools that did not participate (control schools). During a predicted week of peak influenza activity in each state, all households with children in intervention and control schools were surveyed regarding demographic characteristics, influenza vaccination, and outcomes of influenza-like illness during the previous 7 days. RESULTS In all, 47% of students in intervention schools received live attenuated influenza vaccine. As compared with control-school households, intervention-school households had significantly fewer influenza-like symptoms and outcomes during the recall week. Paradoxically, intervention-school households (both children and adults) had higher rates of hospitalization per 100 persons than did control-school households. However, there was no difference in the overall hospitalization rates for children or adults in households with vaccinated children, as compared with those with unvaccinated children, regardless of study-group assignment. Rates of school absenteeism for any cause (based on school records) were not significantly different between intervention and control schools. CONCLUSIONS Most outcomes related to influenza-like illness were significantly lower in intervention-school households than in control-school households. (ClinicalTrials.gov number, NCT00192218.)