(HealthDay News) – Hepatitis A vaccine-induced seropositivity, noted after vaccination of infants younger than 2 years, persists for at least 10 years.

To examine the persistence of seropositivity conferred by hepatitis A vaccine administered to infants, and whether maternal antibodies to hepatitis A virus (maternal anti-HAV) lower the immune response, Umid M. Sharapov, MD, from the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues randomly assigned 197 infants and young children to receive a two-dose hepatitis A vaccine at 6 and 12 months (group 1); 12 and 18 months (group 2); and 15 and 21 months (group 3). Within each group, infants were randomized based on their maternal anti-HAV status and were followed for 10 years after the second dose.

The researchers found that, one month after the second dose, children in all groups had evidence of seroprotection, and seroprotective anti-HAV levels persisted in most children at 10 years. The highest geometric mean concentration at 10 years was seen in children born to anti-HAV-negative mothers in group 3, while the lowest geometric mean concentration was seen for children born to anti-HAV-positive mothers in group 1. Through 10 years of follow-up, anti-HAV levels correlated with initial peak anti-HAV levels (tested at one month following the second dose).

“In conclusion, our study demonstrates that seropositivity to hepatitis A persists for at least 10 years after primary vaccination with two-dose inactivated HAV vaccine when administered to children at ages >12 months, regardless of their mothers’ anti-HAV status,” the authors write.

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