Purpose: The 2009 worldwide influenza A/H1N1 pandemic particularly affected younger people, including schoolchildren. We assessed the effects of class/school closure during the pandemic on the spread of H1N1 infection in Japan.
Methods: We prospectively monitored 2,141 schoolchildren in 57 classes at two elementary schools and two junior high schools in Japan, and evaluated the effects of class/school closures on the spread of H1N1 using descriptive epidemiological methods.
Results: The cumulative rate of H1N1 infection among these children was 40.9% (876 children). There was a total of 53 closures of 40 classes, including school closures, during the pandemic. Time-course changes in the epidemic curve showed that school closure reduced the following epidemic peak more than class closure. A Poisson regression model showed that a longer duration of closure was significantly related to decreased H1N1 occurrence after the resumption of classes.
Conclusions: School closure more effectively inhibits subsequent epidemic outbreaks than class closure. Longer school closures are effective in reducing the spread of infection, and school closure should be implemented as early as possible.