Setting up a Network to Estimate Influenza Vaccine Effectiveness in Latin America, 2013-2017

As of 2018, 40 (77%) of 50 countries/territories in Latin America and the Caribbean have established policies for seasonal influenza vaccination. Despite high coverage levels among the high-risk groups targeted for vaccination, these countries have not routinely measured influenza vaccine effectiveness (VE). We aimed to estimate VE in preventing influenza-associated severe illness among young children and the elderly in Latin America to demonstrate the value of current vaccination strategies and sustain investments in influenza vaccines. We built on the existing severe acute respiratory infections (SARI) surveillance platforms, integrating data from immunization programs to conduct a multi-country case test-negative control study at 123 sentinel hospitals during 2013–2017 in Argentina, Brazil, Chile, Colombia, Costa-Rica, Honduras, El Salvador, Panama, and Paraguay. Surveillance staff identified children aged six months‒2 years and adults aged ≥60 years (both eligible for influenza vaccination provided free of charge by immunization programs) among patients hospitalized with SARI and collected a respiratory specimen from them within ten days of illness onset. Cases were SARI case-patients with influenza virus infection confirmed by reverse transcription polymerase chain reaction (RT-PCR); controls were SARI case-patients RT-PCR negative for influenza viruses. An individual was considered vaccinated if he/she had documented proof of vaccination during the most recent influenza vaccination campaign/season and at least 14 days before the onset of symptoms. We defined full vaccination as the receipt of one dose among adults, and children aged ≤2 years if previously vaccinated; two doses were required for full vaccination of vaccine naïve children aged ≤2 years. All countries used trivalent inactivated influenza vaccines. We used a two-stage random effects model to estimate pooled VE per target age group (children or older adults), adjusting for calendar time (month of i
Doctorat en Santé Publique
info:eu-repo/semantics/nonPublished