Seroprevalence of hepatitis A in adolescent students: A cross-sectional study in Curitiba, Paraná, 2024

Abstract Objective: 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. Methods: A cross-sectional study based on a serological survey was conducted between July 3 and 5, 2024 in five state schools. Stratified random sampling was proportional to the total number of students per school. Adolescents aged 10-19 years were included with individual and legal guardian consent. Collection was conducted in the schools and the samples were analyzed by chemiluminescence for anti-HAV antibodies detection. Information on vaccination was obtained from the municipality’s database. Statistical analyses included calculation of proportions, chi-square tests, and Fisher’s exact test. Results: Of the 216 samples, 35 (16.2%; 95%CI 11.9; 21.7) were reactive for anti-HAV IgG, indicating previous immunity; none of the samples showed reactive IgM. IgG prevalence among the unvaccinated was 4.6% and 11.6% among the vaccinated. Of the 25 previously vaccinated reactive cases, all were in the 10-14 years age group. Of the ten reactive by natural exposure, five were in the 10-14 years age group and five in the 15-19 years age group. IgG seroprevalence showed no significant difference by gender (p-value 0.685) or school (p-value 0.078). Conclusion: Seroprevalence of anti-HAV IgG among adolescents in Curitiba was low, predominating vaccine immunity over that acquired by natural exposure, and absence of acute infection cases.