By NICHOLAS BAKALAR
A series of hepatitis B vaccinations is a routine part of a child’s vaccination schedule, but no one knows how long immunity lasts among children born to healthy mothers. So researchers decided to measure immunity indirectly by testing the response to a booster shot in 378 healthy children and adolescents who had received hepatitis B vaccinations in infancy.
Over all, 99 percent of the children ages 5 to 7 and 83 percent of those ages 10 to 15 who received a recombinant hepatitis B vaccine responded to the booster, meaning that they showed continuing immunity. Among adolescents who had received a plasma-derived vaccine, 69 percent had an antibody response to the new shot. The older the children were, the more likely their immunity was waning: 97 percent of 5-year-olds had an antibody response, compared with 60 percent of 14-year-olds.
The scientists, writing in the August issue of Pediatrics, said the findings did not mean that children were widely becoming susceptible to hepatitis B infection.
“Newer hepatitis B vaccines with higher doses are given to children today,” said Dr. Anthony E. Fiore, a co-author of the study and researcher at the Centers for Disease Control and Prevention. “There are very low rates of hepatitis B right now among adults and children compared to the 1980s, an indication that the vaccine program continues to work. But we’re continuing to study this to make sure that we don’t see any increase in infection in people who were vaccinated as young children.”
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