Cost-effectiveness of the hepatitis B birth-dose vaccine in South Africa: a mathematical modelling analysis

BACKGROUND: In 2022, South Africa had an estimated hepatitis B prevalence of 4·7-6·0%. In an effort to eliminate viral hepatitis as a public health threat, a targeted (ie, selective) hepatitis B birth-dose vaccination (HepB-BD) policy was introduced in 2023. Under this policy, only infants born to mothers with confirmed hepatitis B positivity are eligible for HepB-BD, which is given in addition to peripartum antiviral prophylaxis (PAP) for mothers from the second or third trimester of pregnancy. This policy differs from the WHO recommendation that all newborns should receive a HepB-BD vaccine (ie, a universal HepB-BD policy). We aimed to assess comparative costs and benefits of this and alternate policies in South Africa. METHODS: A validated model of transmission, disease progression, and mortality was used to simulate the ongoing hepatitis B epidemic in South Africa. We projected outcomes from the current South African policy (ie, selective PAP plus selective HepB-BD), a universal HepB-BD-only policy, and the WHO-endorsed selective PAP plus universal HepB-BD policy. Health and economic impacts were compared with a baseline of no HepB-BD coverage, over a 2025-100 time horizon. Costs were reported in consumer price index-adjusted 2024 ZAR and outcomes discounted at 3% per annum. FINDINGS: The current South African HepB-BD policy required fewer vaccinations per outcome averted, with the number needed to vaccinate per vertically acquired chronic hepatitis B infection averted found to be six (95% uncertainty interval 3-15), compared with 462 (223-1479) under a universal HepB-BD-only policy or 77 (38-240) under a selective PAP plus universal HepB-BD policy. Despite incurring the greatest programmatic costs, a selective PAP plus universal HepB-BD policy averted the greatest disease burden and was modelled to be the most cost-effective option at a willingness-to-pay threshold of 0·5 × per-capita gross domestic product (ZAR 57 281). INTERPRETATION: Our findings support implementation of a universal HepB-BD policy alongside South Africa's current hepatitis B viral transmission elimination efforts. FUNDING: Vaccine Impact Modelling Consortium.