BACKGROUND: In Ethiopia, hepatitis B virus infections are prevalent and highly endemic. Additionally, there has been a significant increase in hospital admissions, morbidity, and mortality associated with hepatitis B virus infections. This study aimed to assess the prevalence of hepatitis B virus infection and associated factors among adult intrafamilial household contacts of pregnant women index cases attending antenatal care clinics in the central Ethiopian region. METHODS: A community-based cross-sectional study was conducted between October 1, 2023, and March 1, 2024. Three hundred eighty-five adult intrafamilial household contacts were randomly selected via lottery methods. A 3 ml venous blood sample was taken from adult intrafamilial household contacts and checked for hepatitis B virus infection through hepatitis B surface antigen. An interviewer-administered questionnaire was used to collect the data. A logistic regression model predicted the relationship between predictor and outcome variables. A p-value of <
0.05 indicated statistical significance. RESULTS: The overall response rate was 96.1%. Two-thirds of the adults of intrafamilial household contacts (n = 229
61.9%) were aged between 18 and 28 years, with a mean age of 28 years. The prevalence rate of hepatitis B virus infection among adults of intrafamilial household contacts with pregnant women as the index case was 11.6% (95% CI, 8.6 to 15.1). Being male (AOR: 0.09
95% CI: 0.03, 0.37) and a duration of stay with the index case of less than six months (AOR: 0.30
95% CI: 0.11, 0.81) were associated with a reduced risk of hepatitis B virus infection. Meanwhile, large family sizes (≥ 7) (AOR: 4.32
95% CI: 1.34, 13.98), genital discharge (AOR: 3.14
95% CI: 1.60, 6.15), engagement in unsafe sex (AOR: 2.37
95% CI: 1.13, 4.97), and a history of mortality due to hepatitis in the family (AOR: 3.03
95% CI: 1.09, 8.42) were associated with an increased risk of hepatitis B virus infection. CONCLUSION: This study found that hepatitis B surface antigen seropositivity among adult intrafamilial household contacts with pregnant women index cases in the central Ethiopia region was high at 11.6%. These findings suggest that interventions to prevent HBV infection should prioritize educational campaigns targeting adult intrafamilial household contacts of HBV-positive index cases, focusing on risk factors associated with HBV transmission, prevention, counselling, testing, and vaccination.