Multicenter Evaluation of the Effectiveness of Seasonal Influenza

Influenza is responsible for a sizable burden of disease in the countries of Latin America and the Caribbean, particularly in the risk groups targeted for vaccination. Major progress has been made in introducing the influenza vaccine and achieving adequate vaccination coverage in most of the countries in the Region. So far, however, very few evaluations of its effectiveness have been published. Effectiveness of the vaccine depends on several factors, including age and health of the person receiving it, the type of vaccine used, and the match between vaccine strains and circulating strains, which vary from one influenza season to the next. It is therefore necessary to know how well the vaccine is performing each year to assess the impact of vaccination, guide complementary prevention and control measures during seasons when the vaccine’s effectiveness is low, and gain an idea of the vaccination program’s impact over the medium term while still allowing for variations from one year to the next.