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Early results from two major COVID-19 vaccine trials have sparked hope that the worst of the pandemic may soon be over. But it’s still unclear if or when that relief would extend to pregnant people, who have been excluded from those vaccine trials. 

Pfizer and Moderna, which are developing two high-profile vaccine candidates, have posted initial data from their large late-stage trials that suggests their products could be close to 90 or 95 percent effective in reducing risk of COVID-19 infection. Moderna’s data also suggests its vaccine would reduce the risk of severe illness caused by the coronavirus. 

Both companies have indicated they will seek a federal emergency-use authorization, in which the government makes the drug available before having approved it, based on the strength of early results. That means vaccines could be available to the general public by next spring. 

But since the vaccine trials have thus far excluded people who are pregnant or breastfeeding, it’s unclear when the immunizations would be safely available for them. 

The exclusion has sparked concern from health experts, especially since research from the Centers for Disease Control and Prevention has made it clear that pregnancy significantly increases COVID-19’s mortality risk. Pregnant people are also more likely to develop complications and require intensive medical care, including requiring a ventilator.

“Pregnant women are now squarely in the higher risk population, which makes thinking about a vax for them — it was already a pressing concern, but it’s even more pressing,” said Anne Lyerly, obstetrician and bioethicist at the University of North Carolina-Chapel Hill’s department of social medicine.

Pfizer spokesperson Jerica Pitts said the company is working on a “potential pathway” to a pregnancy-related indication for the vaccine program, which would mean getting the vaccine approved for use during pregnancy. It is also currently doing early research — not yet conducting trials in humans — to see how the vaccine works in pregnancy, Pitts said.

Moderna has not specified its plans to research the vaccine in pregnant people. The company did not respond to The 19th’s requests for comment.

The federal Food & Drug Administration, which will determine whether either vaccine candidate gets an emergency authorization, could approve the vaccine for all healthy adults — which would then allow health authorities like the CDC to determine whether pregnant people should be eligible to get the immunization or if they will have to wait until one is specifically tested for them. The FDA could also approve a vaccine for healthy adults but specifically advise against giving it to pregnant people, at least temporarily.

Experts are still debating when vaccines should in general be tested on those who are pregnant. Historically, major vaccines have not been tested during pregnancy, because of concerns that both the pregnant person and fetus would be at risk for complications. But that thinking has shifted in recent years — particularly in light of the Ebola crisis, when, similarly to COVID-19, vaccines were not initially tested for pregnant people even though they were at severely heightened risk of mortality.  

Some researchers, following conventional wisdom, say later is better, when vaccines have been proven to be safe in pregnancy. But many others note that delaying when to include pregnant people in trials, as Moderna and Pfizer have done, will put them at risk. 

“We need data collected in a systematic way to guide pregnant women and their health care providers regarding whether they should get a COVID-19 vaccine,” said Sonja Rasmussen, a 20-year CDC veteran and professor of pediatrics and epidemiology at the University of Florida.

Excluding those who are pregnant, she added, means much of the vaccines’ risks and benefits are still a question mark. 

“Many questions need to be answered,” she said. “Is the vaccine effective during pregnancy? Is a different dose needed during pregnancy? Is the vaccine safe for the pregnant woman and her fetus? Will the vaccine provide some degree of protection to the newborn infant?”

The FDA typically recommends pregnant people be included in late-stage trials. In its COVID-19 recommendations, the FDA advised companies to at least consider including those who are pregnant in vaccine trials, and in July, National Institutes of Health Director Frances Collins said inclusion of pregnant people in vaccine trials was “a top priority.” 

Some Democratic lawmakers have also called on major vaccine companies to include pregnant people in their trials or otherwise ensure immunizations are available to them. Sen. Elizabeth Warren and Rep. Lauren Underwood introduced legislation to this effect in August.

Women of childbearing age are also disproportionately represented amongst frontline worker groups, including health care professionals and teachers — the very people who experts say need to receive the vaccine first.

“A significant number of health workers are women. Within that there are always, at any given time, a substantial number who are pregnant,” said Ruth Faden, a bioethicist at Johns Hopkins University who focuses on immunizations for pregnant people. “What’s the right ethics stance towards a pregnant health worker?”

Without good data, it’s difficult to know what the implications are for giving pregnant people either vaccine. But the mechanism underlying both vaccines — a new messenger RNA technology that helps the body develop antibodies to fight the coronavirus — has not been shown to cause harm during pregnancy, Lyerly said. 

This gives her “reason for optimism” that even without being tested on pregnant people, the vaccine could be used to protect them, she said. 

“The heightened awareness of the needs to protect pregnant women is a relatively recent phenomenon,” she said. “A focus on the needs to protect them through vaccination — not just from the risks of an intervention like a vaccine — that’s an important shift.”