CD40LG and infection: <h4>Objective</h4>Estimate the seroprevalence of antibodies against Hepatitis A Virus (anti-HAV)-Immunoglobulin G (IgG) and Immunoglobulin M (IgM)-among adolescent students in Curitiba, Paraná, in the context of an outbreak, and identify the proportion of natural infections and vaccine immunity.<h4>Methods</h4>A cross-sectional study based on a serological survey was conducted between July 3 and 5, 2024 in five state schools.