Abstract
The immune system becomes less effective with age, and older age is associated with an increased susceptibility to diseases and reduced responses to vaccination. Furthermore, some adult populations, such as those with diabetes mellitus, are at increased risk of acute hepatitis B virus (HBV) infection. Decreasing responses to vaccination with advanced age have been described, but it is not known at what age immunogenicity starts to reduce, or until what age immunogenicity remains acceptable (for example ≥ 80% seroprotection post-vaccination). We characterized the relationship between age and seroprotection rate induced by recombinant HBV vaccination by conducting a pooled analysis of clinical trial data. Healthy adults aged ≥ 20 y who had been vaccinated with 20 μg HBV vaccine (Engerix™ B, GSK Vaccines, Belgium) in a 0, 1, 6 months schedule in 11 studies since 1996 were included. The observed seroprotection rate, defined as an anti-HBV surface antigen antibody concentration ≥ 10 mIU/ml was 94.5% in the whole population (N = 2,620, Total vaccinated cohort), ranging from 98.6% in adults vaccinated at age 20-24 years, to 64.8% in those vaccinated at age ≥ 65 y A model on seroprotection rates showed a statistically significant decrease with age, and predicted that the anti-HBs seroprotection rate remains ≥ 90% up to 49 y of age and ≥ 80% up to 60 y of age. Individuals at risk of HBV infection should be vaccinated as early in life as possible to improve the likelihood of achieving seroprotection. Additional studies are needed to identify whether unvaccinated individuals older than 60 y would benefit from regimens that include additional or higher vaccine doses.