The predicted pattern of emergence of vaccine-resistant hepatitis B: a cause for concern?

We develop an epidemiological model of hepatitis B virus (HBV) in The Gambia in order to investigate the possible patterns of emergence of a vaccine-resistant strain. Under pessimistic assumptions (e.g., the current vaccine provides no cross-immunity against the variant) the model predicts the variant will not become dominant over the wild-type for at least 50 years. Therefore the current low prevalence of variant infections is not evidence for high cross-immunity of the vaccine or for low infectiousness of the variant, but may simply be a consequence of the epidemiology of HBV. The efficacy of the present vaccine against possible variants needs to be evaluated now to determine whether vaccine modifications are required. However, the model also suggests that serological surveillance may be unable to determine this efficacy for 40-50 years.