Long-Term Persistence of Hepatitis A Virus Immunity in Healthcare Workers Upto 25 Years After Vaccination

Hepatitis A virus (HAV) remains globally endemic, particularly in populations with limited sanitation and poses risks to travellers and healthcare personnel. Although vaccination provides long-term protection, data on the duration of immunity in occupationally exposed groups are limited. We conducted a prospective cohort study among healthcare personnel and medical students vaccinated with either a monovalent HAV vaccine (Havrix, Avaxim) or a combined HAV/HBV vaccine (Twinrix) between 1996 and 2003 at Bari University Hospital, Italy. Vaccination records were verified, and serum anti-HAV IgG concentrations were quantified using CMIA (ARCHITECT HAVAb-IgG). Statistical analyses included Student's t-test, χ² test and logistic regression (STATA MP 11). A total of 334 participants were included (167 per group; mean age 31 vs. 36 years). After a median of 23 years since vaccination, seroprotection rates were 94.6% for the monovalent and 97.0% for the bivalent vaccine groups (p = 0.28). Mean anti-HAV IgG concentrations were significantly higher in the bivalent vaccine group (10.9 ± 4.6 IU/mL) than in the monovalent group (8.3 ± 4.6 IU/mL; p < 0.001). No associations were observed with sex or behavioural factors, and younger age was the only independent predictor of higher antibody levels (β = 0.32; 95% CI, 0.10-0.43; p < 0.001). These findings demonstrate that protective HAV antibody levels persist for more than two decades after vaccination. Both monovalent and bivalent vaccines confer durable immunity, supporting the continued inclusion of HAV vaccination in national immunisation programs and occupational health strategies.