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Introduction <p>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.</p> Methods <p>A cohort of healthy toddlers from Mendoza, Argentina, who received one (<i>N</i> = 436) or two (<i>N</i> = 108) doses of the inactivated HAV vaccine (Avaxim<sup>®</sup> 80U Pediatric), were followed for up to 15&#xa0;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&#xa0;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&#xa0;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.</p> Results <p>At year&#xa0;15, anti-HAV antibody geometric mean concentrations (GMCs) were 73.7 (95% CI 65.0–83.6)&#xa0;mIU/ml and 291.1 (95% CI 226.1–375.0)&#xa0;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&#xa0;years post-vaccination, GMCs were predicted to be 51.8 (95% CI 36.8–75.1)&#xa0;mIU/ml and 134.7 (95% CI 84.5–221.1)&#xa0;mIU/ml after one and two vaccine doses, respectively, with seroprotection rates of 94% (95% CI 89–98) and 93% (95% CI 88–97).</p> Conclusions <p>The HAV vaccine, Avaxim<sup>®</sup>, administered as one- or two-dose schedule, elicited long-lasting immunity in children, with a single dose sufficient to ensure long-term protection.</p>

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

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月12日

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  • Carlos Espul,
  • Héctor Horacio Cuello,
  • Ana Saravia,
  • Marcos Emmanuel Vargas,
  • Catherine Bravo,
  • Christèle Augard,
  • Laurent Coudeville

摘要

Introduction

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.

Methods

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.

Results

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).

Conclusions

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.