Objective: To estimate the prevalence of hepatitis B virus (HBV) infection and vaccine-induced immunity in the region of Madrid, and to analyze their evolution over time. Methods: An observational, analytical, cross-sectional study was carried out in the population aged 16-80 years between 2008 and 2009. This was the last of four seroprevalence surveys in the region of Madrid. The prevalence of HBV infection and vaccine-induced immunity was estimated using multivariate logistic models and were compared with the prevalences in the 1989, 1993 and 1999 surveys. Results: In the population aged 16-80 years, the prevalence of HBV infection was 11.0% (95% CI: 9.8-12.3) and that of chronic infection was 0.7% (95% CI: 0.5-1.1). The prevalence of vaccine-induced immunity in the population aged 16-20 years was 73.0% (95% CI: 70.0-76.0). Compared with previous surveys, there was a decrease in the prevalence of HBV infection. Conclusions: Based on the prevalence of chronic infection (andlt;1%), Madrid is a region with low HBV endemicity. Preventive strategies against HBV should especially target the immigrant population.
