Hepatitis B screening among asylum seekers: a retrospective cohort study in Modena, Northern Italy.

Hepatitis B virus remains a major health challenge among migrants from high-endemic regions arriving in low-endemic countries like Italy. However, more evidence on both infection burden and immunity gaps among asylum seekers is needed to inform prevention policies. We conducted a retrospective cohort study of 739 asylum seekers screened for Hepatitis B virus (HBV) in Modena, Northern Italy, between 2019 and 2023. Serological testing included quantitative determination of HBsAg, HBcAb, and HBsAb, allowing identification of active infection, natural immunity, vaccine-induced immunity, and susceptibility. Demographic characteristics, geographic origin, and migration routes were analyzed in relation to HBV status. Participants were predominantly male (94.7%), with a mean age of 27.2 years, and originated mainly from South Asia (59.4%) and Sub-Saharan Africa (26.1%). Overall HBsAg prevalence was 4.1%, substantially higher than what reported for the Italian general population (<1%). Prevalence was highest among Sub-Saharan African migrants (7.3%), who also showed the greatest proportion of natural immunity (36.3%), while South Asian migrants had a prevalence of 3.6% and Northern African migrants null. Among HBsAg-negative individuals, 57% were susceptible to HBV infection, particularly those from South Asia and Northern Africa. Susceptibility was associated with male sex (OR 4.08, 95% CI 1.34-12.44) and age ≥25 years (OR 2.38, 95% CI 1.40-4.04), consistent with birth before the introduction of universal HBV vaccination in many countries. Most HBsAg-positive individuals reported transit through Libya. Asylum seekers in Italy show a high prevalence of HBV infection alongside substantial immunity deficits. Systematic screening and targeted catch-up vaccination should be prioritized within migrant health services as a key public health intervention.