Abstract Body

In Cambodia, the prevalence of HBV infection among pregnant women, children aged 5 to 7 years, and those born to HBsAg-positive mothers was estimated at 4%, 0.6%, and 10%, respectively. While vaccination coverage is satisfactory, management of HBV infection during pregnancy is limited.

The objective was to evaluate the effectiveness of a strategy to prevent HBV MTCT based on: 1/the use of HBsAg/HBeAg RDTs algorithm to screen pregnant women and assess TDF eligibility 2/a TDF treatment from 24 weeks of amenorrhea for those eligible, 3/an early vaccination for all infants at birth (<2 hours of life). Positive HBsAg pregnant women were enrolled in a multicenter interventional prospective study. Women HBeAg-positive or HBeAg-negative & ALT?40 IU/L in a second phase, received TDF from 24 weeks of amenorrhea to 6 weeks postpartum. Infants received hepatitis B birth-dose vaccine in delivery room (< 2 hours of life) then at 6, 10 and 14 weeks of age. HBIg were not recommended but could be done if accessible. The primary endpoint was the proportion of infants with plasmatic HBsAg positivity at 6 months of life, confirmed by HBV DNA detection.

From October 2017 to December 2019, 21,251 pregnant women were screened for HBsAg, 1,339 were positive, 1,194 enrolled in the study and 338 TDF-eligible. At enrollment, median age was 29 years and median gestational age 23 weeks. The median HBV DNA level was 7.9 log10 IU/mL for TDF-eligible women and 2.5 log10 IU/mL for TDF-ineligible women. The proportion of eligible women starting TDF was 94% and 14.5% were treated less than 4 weeks prior delivery. The proportion of women with HBV DNA at delivery < 5.3 Log10 IU/mL was 90% for those treated more than 4 weeks as compared to 50% for those treated less (p<0.001). At birth, 86% of infants received the first dose of vaccine ?2 hours of life, 95% ?24 hours of life and 15% received HBIg. Overall, HMB MTCT rate was 1.26% [0.34%-3.20%] and, in absence of HBIg, 1.48% [CI95%, 0.40-3.74] for TDF-eligible women: 0% [CI95%, 0-1.41] for those treated more than 4 weeks before delivery and 8.33% [CI95%, 1.75-22.5] for those treated less than 4 weeks. For TDF-ineligible women, the transmission rate was 0.98% [0.40-2.02] and 1.06% [CI95%, 0.39-2.30] in absence of HBIg.

An HBIg-free strategy was effective to prevent HBV MTCT if TDF was administrated for at least 4 weeks before delivery. This strategy could allow decentralization of HBV PMTCT to rural areas where most of pregnancies are managed.