Antenatal hepatitis B virus sero-prevalence, risk factors, pregnancy outcomes and vertical transmission rate within 24 months after birth in a high HIV prevalence setting

BACKGROUND: Despite the availability of an effective vaccine, chronic hepatitis B virus (HBV) infections remain a major cause of liver cirrhosis and hepatocellular carcinoma. HBV burden in pregnancy, risk factors and the timing of mother to child transmission remain poorly described especially during this era of lifelong use of Tenofovir/Lamivudine/Efavirenz as firstline for HIV treatment. We aimed to determine the burden of HBV in pregnancy and infants receiving their first dose of HBV vaccine 6 weeks after birth in a high HIV-prevalence setting. METHODS: Pregnant women ≥ 20 weeks’ gestational age were enrolled and followed up as mother-infant dyads from delivery, 6, 24 and 96 weeks after birth. HBV surface antigen (HBsAg) was tested (fresh plasma, immunochromatography) in pregnancy. Women testing HBsAg-seropositive were further evaluated for other four HBV-biomarkers. Maternally HBV exposed babies were tested for HBsAg from birth and HBs-antibodies from 6 months of age. Maternal-infant factors were tested in univariable and multivariable analyses for predictors of HBsAg-seropositivity. RESULTS: Six hundred HIV-uninfected and 608 HIV-infected women on Tenofovir/Lamivudine/Efavirenz-regimen with median (interquartile range) 350: (87–1477) days of therapy use were enrolled. The overall HBsAg-seroprevalence was 32/1208: 2.65%, 95% confidence interval (CI) [1.74, 3.55]; being 7/600: 1.17%, 95% CI [0.37, 1.97] and 25/608: 4.11%, 95% CI [2.52, 5.68] in HBsAg-monoinfected and HBsAg/HIV-coinfected respectively, disproportionately detected in 31/32: 96.9%, 95% CI [90.8, 100] women presumably HBV-unvaccinated in infancy. HBV exposed babies tended to be born prematurely (< 37 weeks); 15.2% versus 9.9% in the HBV-unexposed, p = 0.009. In multivariate logistic regression-models with variable elimination, HIV-infection and reported tooth extractions predicted antenatal HBsAg-seropositivity; odds ratios (CI): 3.85 (1.61–10.7) and 2.46 (1.07–5.34), respectively. None of the exposed infants were HBsAg-seropositive neither before nor after 6 weeks of age. No HBs-antibodies were detected in 23.3% of HBsAg-exposed infants at two years despite having successfully completed the HBV vaccination schedule. CONCLUSION: Low and moderate HBV endemics were observed in HIV-uninfected and HIV-infected pregnant women, respectively. This underscores the need to routinely screen for HBV in pregnancy, especially the HIV-infected attending antenatal-care. Being HIV-infected and reported tooth extractions were independent risk factors for maternal HBsAg-seropositivity. Vertical and child horizontal transmissions were both absent, probably due to ~ the 50% frequency of antenatal anti-HBe-antibodies observed. Of concern was the absence of anti-HBs-antibodies in 23.3% of fully vaccinated/maternally HBV-exposed infants by two years. Absence of molecular diagnosis may have underestimated HBV burden. TRIAL REGISTRATION: www.clinicaltrials.gov, trial registration number: NCT04087239.