Current vaccine recommendations for hepatitis A were endorsed by the findings of a prospective, randomized study of 183 Alaskan Native adolescents followed from infancy to age 15-16 years.
Study participants were randomly assigned to receive two doses of hepatitis A vaccine on three different schedules: at ages 6 and 12 months (group 1); at 12 and 18 months (group 2); or at 15 and 21 months (group 3). Each group was randomized according to maternal anti-HAV status.
Serum samples were collected from study participants at eight sampling time points from 1 month after the second vaccine until age 15-16 years. Those with anti-HAV levels of at least 20 mIU/mL were considered to be seropositive.
Seropositivity was high through age 10 years in all three groups – 100% in groups 2 and 3, and more than 90% in group 1. After age 10 years, however, seropositivity decreased. At age 15-16 years, 50%-75% of those on the 6 and 12 months’ schedule were seropositive as were 67%-87% of the other two groups whose mothers were anti-HAV-positive. Among those who were seropositive at age 15-16 years, 84% are predicted to remain so for at least another 30 years.
The findings that seropositivity was less frequent among those starting vaccination at age 6 months and among those whose mothers were antibody positive and who started vaccination at age 12 months or 15 months support current vaccine recommendations, Dr. Philip Spradling of the Centers for Disease Control and Prevention and his colleagues wrote.
Read the article in Hepatology ( 2015 Dec 5. doi: 10.1002/hep.28375 ).