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HAV vaccine effective in infants for 10 years regardless of maternal antibodies

Infants and young children who received HAV vaccination remained seropositive for 10 years or longer regardless of the presence of maternal HAV antibodies in a recent study.

Researchers randomly assigned 197 children to receive a two-dose HAV vaccine at 6 and 12 months (group 1), at 12 and 18 months (group 2) or at 15 and 21 months (group 3), and anti-HAV levels were recorded 1 month and 6 months and 3, 5, 7 and 10 years after vaccinations. Each group contained an equal number of patients with and without maternally transferred HAV antibodies.

All evaluable participants had seroprotection (defined as anti-HAV levels greater than 10 mIU/mL) against HAV at 1 month, and most retained that protection through 10 years. Among children in group 1, 7% of children born to anti-HAV-negative mothers and 11% of those with anti-HAV-positive mothers had lost seroprotection at 10 years, as did 4% of children with anti-HAV-negative mothers in group 3.

The differences in geometric mean concentration (GMC) of anti-HAV levels between the three groups were significant at 3, 5 and 7 years among children with anti-HAV-positive mothers, (P<.001 at 3 years, P=.008 at 5 years and P=.015 at 7 years) and at 3, 5, 7 and 10 years among those with anti-HAV-negative mothers (P<.001 at 3, 5 and 7 years and P=.002 at 10 years). Patients in group 1 had smaller GMC values than groups 2 and 3 at all evaluated time points.

Children with anti-HAV-positive mothers had smaller GMC values than those with anti-HAV-negative mothers, but the difference was not significant in most cases.

“Our study demonstrates that seropositivity to hepatitis A persists for at least 10 years after primary vaccination … when administered to children at ages 12 months and older, regardless of their mothers’ anti-HAV status,” the researchers wrote. “ … continued follow-up of hepatitis A vaccine cohorts is warranted to determine whether in the future a booster dose will be necessary to maintain seropositivity. Therefore, we plan to follow this cohort through at least 15 years after initial immunization and thereafter as long as it is feasible.”