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Tenofovir (TDF) prophylaxis for 4 weeks or more, along with early infant vaccination, helped stem hepatitis B virus (HBV) mother-to-child transmission in Cambodia, without use of hepatitis B immunoglobulin (HBIg), a researcher said.

In a cohort of 227 infants born to TDF-eligible pregnant women with HBV, mother-to-child transmission was 0% if TDF was taken for more than 4 weeks prior to delivery, but 8.3% if TNF was taken for less than 4 weeks, reported Olivier Segeral, MD, of the French National Agency for Research on AIDS and Viral Hepatitis, and University of Health Sciences in Phnom Penh, Cambodia.

At a press conference at the virtual Conference on Retroviruses and Opportunistic Infections (CROI), Segeral touted the immunoglobulin-free strategy as a viable option to prevent HBV mother-to-child transmission in low- and middle-income countries where structural barriers prevent access to immunoglobulin.

"Many low- and middle-income countries face difficulty in accessing immunoglobulin and HBV DNA quantification, and the use of immunoglobulin-free regimens was identified by WHO as a research gap," he said.

Segeral said that to his knowledge, this was the first large study to evaluate an immunoglobulin-free strategy to prevent HBV transmission using TDF prophylaxis.

The (Tenofovir As Prevention Of Hepatitis b Mother-to-child Transmission) study was a single-arm prospective trial conducted from October 2017 to November 2020 in five maternity units in Cambodia. Pregnant women who tested positive for hepatitis B surface antigen (HBsAg) were screened during antenatal care with an HBsAg rapid test.

TDF eligibility was determined from October 2017 to December 2017 by testing positive for hepatitis B e antigen (HBeAg) via rapid test, though from January 2019 onward those testing positive for HBeAg via rapid tests and those testing negative for HBeAg but with alanine transaminase at 40 IU/L were eligible.

Infants were vaccinated against HBV at birth, and at week 6, 10, and 14. Segeral added that while HBIg was not recommended, it could be used where available.

Of 1,594 pregnant women, 338 were TNF-eligible, and 88% of infants born to TNF-treated women were vaccinated within 2 hours of birth.

Because one maternity unit did use HBIg, the results were stratified by HBIg use. Among the 271 infants testing positive for HBsAg without use of HBIg, none of the 227 infants whose mothers used TDF for more than 4 weeks tested positive (0.00, 95% CI 0.00-1.61) compared with 8.33% of the 36 infants whose mothers used TDF for less than 4 weeks.

Segeral added that the high transmission rate for women treated with TDF for a shorter period of time "highlights the importance of providing HBV testing as early as possible during pregnancy."

He said these results are "essential for ... low- and middle-income countries where immunoglobulin is limited to national hospitals or private clinics in urban settings" but the majority of pregnant women are treated in a rural setting, and added that this strategy could help to achieve the WHO target of <0.1% HBsAg prevalence in infants in 2030.

CROI Chair Elaine Abrams, MD, of Columbia University Medical Center in New York City, who moderated the session but was not involved with the research, asked Segeral if he thought this study would affect treatment guidelines.

"Are we likely to see a non-HBIg option for the prevention of Hep B in infants or do we need more evidence?" she asked.

Segeral noted that this strategy is already included in Cambodian guidelines, using a therapeutic algorithm where HBV DNA quantification is available, and said he and his colleagues have been in contact with WHO Western Pacific about their strategy.

"Maybe we can discuss with them [how] to include this new strategy in the new WHO guidelines," Segeral said.

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