Vaccine pregnancy trials begin in bid to fill global data void

Pfizer Inc. and German partner BioNTech SE are starting trials for their messenger RNA vaccine in 4,000 women in the latter stages of pregnancy, according to the US online clinical trial registry. The companies will run a mid-stage study for 350 volunteers between 27 and 34 weeks gestation to confirm safety before moving into advanced trials for women between 24 and 34 weeks pregnant.

AstraZeneca Plc. and Johnson & Johnson are planning to run trials in the coming months. It’s good news for pregnant people, who until now have faced a difficult dilemma: excluded from vaccine studies, yet more vulnerable to severe Covid-19. Some studies have also linked the disease to premature birth.

“While it’s good news that vaccine trials in pregnant women are finally beginning, the results from these trials are unlikely to be available before the autumn," said Marian Knight, professor of maternal and child population health at the University of Oxford.

Pregnant women were kept out of vaccine studies due to a lack of safety information and a potentially higher risk of adverse events, despite calls from many scientists and doctors for their inclusion. As a result, the US, UK and World Health Organization have advised against vaccinating pregnant women unless they’re at high-risk, such as front-line health-care workers.

The Pfizer-BioNTech study will be run in the US, Europe, South America and Africa and focuses on the third trimester of pregnancy to minimize risk to unborn children, BioNTech said in an e-mailed statement. The companies aren’t planning to evaluate whether the vaccine could have a preventative effect for babies after birth.

Most companies have also set up registers to monitor participants who conceived after taking part in vaccine trials. Astra and partner Oxford told a US panel in January that 21 women from the trials had become pregnant after vaccination, while 23 women from the Pfizer-BioNTech studies reported last year they were expecting.

Andrew Pollard, lead investigator on the Oxford-Astra UK trials, said the university will report findings once all babies conceived in its study population have been followed up.

Current UK guidance advises a second vaccine dose be delayed if a low risk woman becomes pregnant after the first shot.

Vaccine trials for children also only started in recent months, with the first data expected by summer. While kids don’t generally suffer from severe Covid, they could be key to preventing transmission to vulnerable people, including pregnant women at home.

“It is a gap and it’s one that we’re looking to see how we can address," June Raine, chief executive officer of the UK Medicines & Healthcare Products Regulatory Agency, said at a board meeting Tuesday. “We do appreciate there’s a need for some more robust data."

The US National Institutes of Health said Wednesday it’s beginning a study on the effects of Covid-19 treatment remdesivir in pregnant women. The antiviral drug from Gilead Sciences Inc. has been shown to accelerate recovery from severe disease and was approved by the US for use in Covid-19 patients last year.