Effect of an immunization program on seasonal influenza hospitalizations in Mexican children.

We analyzed 2378 respiratory samples of children <5 years of age admitted during a 7-year period in order to determine the contribution of seasonal influenza as a cause of hospitalizations, as well as the impact of the inclusion of influenza vaccine in the childhood immunization program. The presence of influenza virus was demonstrated in 106 (4.4%) samples. The proportion of influenza hospitalizations after the introduction of influenza vaccination was lower (3.4%) than before the establishment of this vaccination program (7.5%; P=0.00002). Our study shows that influenza vaccination programs in children significantly reduce the impact of influenza related hospitalizations.