Public Health

Hepatitis A antibodies persist for decades after vaccination

Last Updated: 2009-01-06 15:49:16 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Hepatitis A virus antibodies (anti-HAV) persist for nearly 30 years after vaccination, a finding that may affect current hepatitis A immunization protocols.

Investigators from the Centers for Disease Control and Prevention in Atlanta and the Alaska Native Tribal Health Consortium in Anchorage report their findings in the December 15th issue of The Journal of Infectious Diseases.

Lead author Dr. Laura L. Hammitt, now at the Kenya Medical Research Institute/Welcome Trust Collaboration in Kilifi, and colleagues enrolled 144 children and 128 adults who responded to a three-dose series of hepatitis A vaccine to assess the persistence of anti-HAV.

Adults had received a primary dose of 720 ELISA units of hepatitis A vaccine, with a second vaccination given 1 month later and a third vaccination given 12 months after the first (0-1-12 months).

The children were between 3 and 6 years of age and had received one of three hepatitis A vaccination schedules:

- A first dose of 360 ELISA units followed by a second and third vaccine 1 and 2 months later (0-1-2 months);

- 360 ELISA units with the second and third vaccines given 1 and 6 months later (0-1-6 months); or

- 360 ELISA units with the second and third vaccines given 1 and 12 months later (0-1-12 months).

Dr. Hammitt's team collected serum specimens 1 month after vaccination and again 1 to 10 years after vaccination to test for anti-HAV by ELISA. The researchers estimated long-term antibody persistence by using the observed rate of decline in geometric mean concentration.

All children tested at 10 years and 96% of adults tested 8-9 years after immunization had detectable anti-HAV.

"The estimated duration of antibody persistence was 21-27 years, depending on the vaccination schedule," Dr. Hammitt and colleagues note.

Children vaccinated on the 0-1-12 month schedule had the highest anti-HAV levels.

"Children vaccinated at 0-1-2 months had a significantly lower geometric mean concentration of antibody than children vaccinated at 0-1-12 months, but this difference was statistically significant only through 4 years of follow-up," the CDC team reports.

"The findings of this study document that seroprotective anti-HAV levels are retained for at least 10 years after vaccination. Hepatitis A booster doses after completion of the primary vaccination series do not appear to be warranted and are not currently recommended," the CDC team writes.

"Antibody concentrations do decline over time, and ongoing monitoring is needed to evaluate immunity beyond 10 years after vaccination to assess whether persons vaccinated as children will be protected throughout adulthood."

J Infect Dis 2008;198:1776-1782.