Sexual and reproductive health knowledge and HBsAg positivity among adolescents and young adults in Benguela Province, Angola: a pooled cross-sectional study

Sexual and reproductive health (SRH) knowledge is a key determinant of health outcomes among adolescents and young adults, particularly in low- and middle-income countries. In Angola, young people continue to face substantial SRH challenges, including early childbearing and a high burden of sexually transmitted infections (STIs), yet subnational data remain limited. To characterise SRH knowledge, sexual behaviours, and STI profiles among adolescents and young adults aged 15–25 years recruited in the same four municipalities of Benguela Province in two independent survey rounds conducted using identical study procedures. We conducted a pooled cross-sectional analysis of two independent community-based surveys carried out in 2021 and 2024 in four municipalities of Benguela Province. Participants were recruited using a community-based convenience sampling approach through outreach activities conducted in public spaces, youth centres, and churches. This recruitment strategy was designed to maximise participation among adolescents and young adults in the selected municipalities but was not intended to provide a representative sample of the general population. SRH knowledge was assessed using a structured questionnaire, and point-of-care testing was offered for HIV (Alere Determine HIV1/2 antibodies, Abbott), hepatitis B surface antigen (HBsAg) (HBsAg, Nantong diagnosis Biotech-nology), hepatitis C virus (HCV), and syphilis (Treponema pallidum antibodies, Nantong Diagnos Biotechnology)..Multivariate logistic regression was used to identify factors associated with adequate SRH knowledge and HBsAg positivity, accounting for survey year. A total of 2,802 adolescents and young adults were included. Adequate SRH knowledge was significantly associated with female sex (aOR 1.49, 95% CI 1.23–1.75), older age (aOR 1.06 per one-year increase, 95% CI 1.03–1.09), higher education (aOR 5.30, 95% CI 1.99–14.17), and urban residence (aOR 1.75, 95% CI 1.47–2.10). Participants surveyed in 2024 had lower odds of adequate SRH knowledge than those surveyed in 2021 (aOR 0.61, 95% CI 0.52–0.70). HBsAg positivity was observed in 35% of participants, with substantial variation between the independently recruited survey rounds (approximately 13.6% in 2021 and 56.3% in 2024), whereas HIV, HCV, and syphilis positivity were 1.2%, 0.5%, and 1.0%, respectively. Important inequalities in SRH knowledge were observed among adolescents and young adults in Benguela Province, particularly according to age, educational attainment, and place of residence. The high overall screening-based HBsAg positivity, together with the marked difference observed between the two independently recruited survey rounds, warrants cautious interpretation and further investigation using representative sampling and confirmatory testing alongside strengthened HBV prevention strategies, including vaccination, expanded screening, and integration of HBV services into youth-friendly SRH programmes. These findings underscore the importance of equitable access to SRH information and services to reduce preventable health risks among young people in Angola.