- Category: HBV Vaccines
- Published on Tuesday, 11 September 2012 00:00
- Written by Liz Highleyman
Nearly all children who received 3 doses of the Engerix-B hepatitis B vaccine achieved protective immunity, but about 20% fell below the protective antibody threshold by year 15 and could benefit from a booster shot, Canadian researchers reported at the 52nd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC 2012) this week in San Francisco.
Widespread immunization against hepatitis B virus (HBV) has dramatically reduced the incidence of infection worldwide over the past 3 decades. Many countries now include HBV in their recommended infant vaccine series, and "catch up" vaccination is recommended for adolescents and older people at risk.
Gaston De Serres and colleagues from the Quebec Public Health Institute and Laval University measured anti-HBs antibody levels and immune memory persistence over 15 years in people who were vaccinated prior to adolescence.
Hepatitis B vaccines are highly immunogenic but do not always provide life-long protection, the researchers noted as background. At 1 to 6 months after vaccination, anti-HBs levels are 10- to 100-fold higher than the protective level. But by 5 to 15 years after vaccination, some individuals have antibody levels below the protective threshold -- and in some cases even undetectable. Nevertheless, despite the disappearance of antibodies, it is thought that immune memory ensures continued protection, though it is not known how long this lasts.
This prospective analysis, started in 1995, enrolled 1129 children aged 8 to 10 years who had received the Engerix-B (GlaxoSmithKline) vaccine series in school according to the recommended dosing schedule of 10 mcg intramuscular injections at birth, 1 month, and 6 months.
Participants were then randomly assigned (1:1:1) to receive a booster or challenge dose at either year 5, 10, or 15 of the study. Antibody levels were measured 1-2 months after the third primary vaccine dose, 1-2 months before and after the booster shot, and at 5, 10, and 15 years after initial vaccination. About 220 participants from each booster timing group were included in the final analysis.
- Nearly all participants in all arms had anti-HBs titres > 1 IU/L before they received their booster.
- Nearly 90% of children in the 5-year and 10-year booster arms had antibody levels > 10 IU/L -- generally considered a protective level -- prior to boosting, but the proportion fell to 77% for those who did not get their booster until year 15.
- 68% of children in the 5-year booster arm and 61% in the 10-year booster arm had antibody titres > 100 IU/mL before boosting, falling to 37% in the 15-year booster arm.
- 1 month after receiving their booster, 100% in all groups had antibody levels > 1 IU/L and > 10 IU/L; 98%, 97%, and 96%, respectively, reached >100 IU/L.
"Vaccination of 8-10 year-old children with 3 doses of Engerix-B induces a protective immunity in nearly all (> 98%) vaccines for at least 15 years," the researchers concluded.
"The strong antibody response to a challenge (booster) dose suggests the presence of an excellent immune memory in virtually all responders to primary vaccination," they continued. "The results indicate no need [for a] booster dose for at least 15 years post-primary vaccination" for this population.
V Gilca, N Boulianne, M Dionne, G De Serres, et al. Antibody Persistence and the Effect of a Booster Dose Given 5, 10 or 15 Years After Vaccination With a Recombinant Hepatitis B Vaccine. 52nd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC 2012). San Francisco. September 9-12, 2012. Abstract G-1047.