Cadavid–Betancur DA, et al. – Researchers investigated the seroprevalence of hepatitis B (HB) and of potentially associated factors in Medellin, Colombia, 17 years after the start of universal vaccination. In 2009, Medellín indicated vaccine immunity of 25.1% (95% CI 21.7–28.8). Very low prevalence of chronic infection was observed, only 0.2% (95% CI 0.1–0.7) and there appeared no acute infection. Higher susceptibility was observed in older people. The results may represent a population effect of mass vaccination from 1994. They recommended to complete the vaccination schedule and improve living conditions that could influence vaccine immunity.

• Researchers analyzed biological and sociodemographic data from a population survey with a multistage random sampling in 6–64 year old individuals.
• 2077 samples were tested for HB surface antigen, total HB core antibodies and HB surface antibodies, and in some cases IgM antibodies to HB core antigen.
• Multinomial logistic regression was utilized to assess the factors potentially associated with and natural, and vaccine immunity relative to susceptibility (absence of any marker).  
• Findings revealed that the prevalence of serological patterns was: chronic infection 0.20% (95% CI 0.11–0.71), vaccine immunity 25.10% (95% CI 21.72–28.83) and natural immunity 2.60% (95% CI 1.80–3.74).
• They identified no markers in 71.30% (95% CI 67.70–74.83) of the individuals and gained no evidence of recent infection.
• Relative to the absence of markers, there appeared a potential association of natural immunity with age (6–17 years and 41–64 years) and sleeping less than 6 hours, while vaccine immunity seemed associated with age (6–17 years), reporting vaccination against HB, belonging to high socioeconomic strata, home ownership and being obese, after adjusting for other variables.