In this study, we found the prevalence of hepatitis B surface antigen was 0.46% and the prevalence of HIV antibodies was 0.3% in this community-based cohort of individuals born between 1965 and 1985. These figures appear higher than previously published estimates. As would be expected, approximately two-thirds of those infected were male. A surprise finding was that the prevalence rates of both hepatitis B and HIV were significantly higher in Cork than the other centres combined. We are not aware of a reason for this and it may represent a chance finding. Nevertheless, further investigation is warranted to confirm or refute this finding.

There are limited data on the epidemiology of hepatitis B and HIV in the community in Ireland. A recent publication from the European Centre for Disease Control (ECDC) and Bristol University suggested a population prevalence of 0.21% for HBsAg and a prevalence of 0.26% among prisoners [5]. All pregnant females in Ireland are offered screening for hepatitis B and HIV. The Coombe maternity Hospital in Dublin reported 6974 babies born in 2023. All expectant mothers are checked for hepatitis B, HIV and hepatitis C. Seven were HBsAg positive (0.1%), 18 had HIV (0.26%), 10 had antibodies to hepatitis C but none was PCR positive [6]. The Rotunda Hospital delivered 8442 babies in 2023. Thirty-two had HBsAg (0.38%) and 25 (0.3%) had antibodies to HIV [7]. The prevalence of HBsAg in first time blood donors in Ireland (1999–2022) was very low at 0.009% (monthly donation testing report, UK Health Security Agency). These figures are for donors born in Ireland or the UK, but would constitute a special population as individuals with risk factors are discouraged from donating.

International protection applicants in Ireland are offered blood-borne virus screening as many are from high prevalence countries. Uptake is variable but the national reception centre for international protection applicants, in Balseskin, Dublin, reported that of those tested in 2023, 2.2% were HBsAg positive, 4.3% were HIV positive and 0.3% had chronic hepatitis C infection [8]. The UNAIDS program estimates the prevalence of HIV infection in the general adult population in Ireland in 2023 was 0.3% [9]. All pregnant females are offered antenatal testing for HIV. The national prevalence for 2023 was 0.2% [10]. Only 14% of these were new diagnoses suggesting high rates of previous diagnosis, awareness and treatment in this cohort.

The strengths of this study are that it was community based, with a wide geographical spread and was not targeted at higher risk groups. The major limitation is that the samples were anonymised so we have no clinical information about the infected individuals. It is possible that chance over-representation from higher risk groups may have skewed the results, particularly with regard to Cork, in the southwest of the country.

This study suggests that the epidemiology of hepatitis B and HIV infections is changing in Ireland and that the community prevalence of both is higher than previously estimated. This has implications for screening and service provision. It highlights the importance of up-to-date epidemiological studies, particularly in societies affected by large-scale migration and social changes.