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Long-Term Antibody Persistence After Hepatitis A Vaccination in Healthy Toddlers: Insights from Modeling
Carlos Espul1, Héctor Horacio Cuello1, Ana Saravia1
1Higea Gastroenterological Clinic, Mendoza, Argentina.
Insights
A single dose of the hepatitis A virus (HAV) vaccine provides long-lasting protection in children. This study shows that one dose is sufficient for sustained seroprotection up to 40 years post-vaccination.
Area of Science:
- Immunology
- Vaccinology
- Public Health
Background:
- Argentina pioneered a single-dose hepatitis A virus (HAV) vaccination schedule for children in 2005.
- This study evaluated the long-term antibody persistence following this vaccination strategy.
Purpose of the Study:
- To assess the durability of immune response after one or two doses of the inactivated HAV vaccine (Avaxim®).
- To model and predict long-term antibody persistence and seroprotection up to 40 years post-vaccination.
Main Methods:
- A cohort of 544 children in Argentina received one (n=436) or two (n=108) doses of the HAV vaccine.
- Antibody levels were measured up to 15 years post-vaccination.
- A hierarchical model was used to predict antibody persistence and seroprotection to 40 years.
Main Results:
- At 15 years, all participants remained seroprotected, with higher antibody concentrations in the two-dose group.
- Modeling predicted sustained seroprotection rates of 94% and 93% at 40 years after one and two doses, respectively.
- Geometric mean concentrations (GMCs) at 40 years were predicted to be 51.8 mIU/ml (one dose) and 134.7 mIU/ml (two doses).
Conclusions:
- The inactivated HAV vaccine (Avaxim®) elicits long-lasting immunity in children.
- A single-dose vaccination schedule is sufficient to ensure long-term protection against hepatitis A.
- The findings support the effectiveness of the single-dose strategy implemented in Argentina.
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.
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