Seroprevalence of Hepatitis A Virus among people born before and after implementation of universal vaccination in Argentina

Purpose : In Argentina, Hepatitis A virus (HAV) used to contribute to 90% of acute hepatitis cases affecting the pediatric population. In 2005, a single dose of HAV vaccine was implemented for one-year-old children. However, despite vaccination success, a proportion of cases persists. This study aimed to assess the seroepidemiology of HAV in Argentina, analyzing IgG and IgM antibodies against HAV in a sizable population, both vaccinated and unvaccinated. Methods : This retrospective analysis involved 16,982 patients attending a tertiary-care hospital in Buenos Aires, Argentina. Patients were divided into two groups: those evaluated before vaccination and those suspected of having acute hepatitis. Results : Anti-HAV IgG was detected in 9,403 out of 16,587 (56.7%). A higher rate was observed in those individuals born after vaccine implementation (77.7%) compared to those born before (56.3%), p<0.001. The groups aged 19 to 40 and 41 to 60 exhibited the lowest anti-HAV IgG rates. Out of the 3,956 patients assessed for acute hepatitis, 100 (2.5%) tested positive for Anti-HAV IgM. Remarkably, none of the patients covered by mandatory vaccination showed positive Anti-HAV IgM. Conclusions : This large study outlines the seroepidemiology status of HAV in Argentina and underscores the impact of vaccination in reducing infections. Despite the success of the vaccine, certain groups of susceptible individuals still persist, particularly among unvaccinated adults. These findings reveal the importance of targeting vaccination campaigns towards the most vulnerable age groups and emphasize the effectiveness of universal vaccination in reducing the incidence of HAV. This comprehensive analysis provides essential insights for public health planning and guides future immunization strategies against HAV in Argentina.