Work

Long-Term Antibody Persistence After Hepatitis A Vaccination in Healthy Toddlers: Insights from Modeling

Year: 2025

Type: article

Abstract: Argentina was the first South American country to adopt a single-dose hepatitis A vaccine for 1-year-old children, replacing the standard two-dose regimen in the immunization program in 2005. Here, we assessed the long-term persistence of anti-hepatitis A virus (HAV) antibodies following vaccination. A cohort of healthy toddlers from Mendoza, Argentina, who received one (N = 436) or two (N = 108) doses of the inactivated HAV vaccine (Avaxim® 80U Pediatric), were followed for up to 15 years post-vaccination to assess the persistence of anti-HAV antibodies. Three assays were used to measure anti-HAV antibody concentrations, depending on commercial availability. At year 15 follow-up, 161 and 48 participants who received one and two vaccine doses, respectively, without additional booster, remained in the study. Using all available data, we modeled long-term antibody persistence to project immunity to 40 years after vaccination. Antibody persistence was predicted using a hierarchical model that estimated both participant- and group-specific antibody decay, accounting for assay changes over time and natural boosting from virus exposure. At year 15, anti-HAV antibody geometric mean concentrations (GMCs) were 73.7 (95% CI 65.0–83.6) mIU/ml and 291.1 (95% CI 226.1–375.0) mIU/ml among those who received one and two vaccine doses, respectively, and all remained seroprotected. Of the four model specifications tested, the log-logistic model with natural boosting provided the best fit to the observed antibody GMCs and seroprotection rates. At 40 years post-vaccination, GMCs were predicted to be 51.8 (95% CI 36.8–75.1) mIU/ml and 134.7 (95% CI 84.5–221.1) mIU/ml after one and two vaccine doses, respectively, with seroprotection rates of 94% (95% CI 89–98) and 93% (95% CI 88–97). The HAV vaccine, Avaxim®, administered as one- or two-dose schedule, elicited long-lasting immunity in children, with a single dose sufficient to ensure long-term protection. This study examined whether a single dose of the hepatitis A vaccine given to children at 12 months of age would be enough to provide long-term protection against hepatitis A. A group of children from Mendoza, Argentina, who received one or two doses of the inactivated hepatitis A vaccine as part of routine immunization between 11 and 23 months of age were followed for up to 15 years to measure their antibody levels against hepatitis A. Using the antibody data collected, we created a model to estimate how long immunity from the vaccine could last. The model predicted that over 90% of the children who received one or two doses of the vaccine would be protected against hepatitis A for up to 40 years after vaccination. These results suggest that a single dose of the vaccine should be enough to provide long-term protection against hepatitis A.

Source: Infectious Diseases and Therapy

DOI: 10.1007/s40121-025-01278-0