We found a significant reduction in the ratio of student to nonstudent cases during the winter school vacation period compared to the weeks before and after the winter break. Nevertheless, the winter school vacation period coincided with the downward phase of the pandemic in Peru. Our simulations based on a simple agestructured transmission model of influenza suggest that the winter school vacation period had a relatively small effect (,10%) on reducing the overall burden of the pandemic. In contrast, school closure interventions implemented during the early phase of the 2009 A/H1N1 pandemic have been associated with a reduction in influenza transmission rate, estimated at 25% in Hong Kong [33] and 29-37% in Mexico [34] .