Pregnant People Haven't Been Part Of Vaccine Trials. Should They Get The Vaccine?

The Food and Drug Administration is likely soon to authorize distribution of the Pfizer-BioNTech COVID-19 vaccine. But the vaccine trials have so far excluded pregnant people.

Among those first in line to get the vaccine, this is a significant exclusion. Three-quarters of health care workers are women, including more than 85% of nurses. The Centers for Disease Control and Prevention estimates 330,000 health care personnel could be pregnant or recently postpartum at the time of vaccine implementation.

Studies have found that pregnant people are at an increased risk of severe COVID-19. As NPR's Richard Harris reported, vaccine researchers don't expect that the shots will put mothers or newborns at risk — but unfortunately, pregnancy-specific data do not yet exist. Studies involving pregnant people are not expected to begin enrollment until the first quarter of 2021.

Why aren't pregnant women part of vaccine trials?

Denise Jamieson is chair of the Department of Gynecology and Obstetrics at Emory University School of Medicine, and is part of the American College of Obstetricians and Gynecologists' working group on COVID-19.

She says pregnant women are systematically excluded from most clinical trials in the U.S. because it makes running the trials simpler: "There are actually very few medications, for example, that are approved in pregnancy because it's easier, basically. It's easier to exclude pregnant women because when you include pregnant women, you have to be concerned about both the woman's health as well as the development of the fetus and baby."

Pregnant women have been given vaccines for decades, she says, with few issues. "We don't generally give live viral vaccines in pregnancy because there's theoretical risk that the live virus could be passed and it infects the fetus," Jamieson says. "But with the exception of smallpox vaccines, there really have been very few problems with vaccines."

The Pfizer and Moderna vaccines both rely on brand-new messenger RNA technology – but Jamieson doesn't see any scientific cause for concern there. With these vaccines, she says, the mRNA basically goes into the muscle cells, provides information to the cells about how to manufacture the spike protein of the SARS-CoV-2 virus, and then the mRNA is rapidly degraded.

"So I can't think of any potential reason or theoretical reason to be concerned about mRNA vaccines in pregnancy, with the one exception of when you give a vaccine and you mount an immune response, you can get a fever. And fever is something that we try and avoid in pregnancy," she says. "So it may be important that if women get a fever, that they treat [it] with acetaminophen, which is what we recommend for fevers in pregnancy."

"Knowing what I know about the [mRNA vaccine's] mechanism of action, I would anticipate that this vaccine should be very safe in pregnancy," Jamieson says.

Ruth Faden, founder of Johns Hopkins University's bioethics institute, says it's not an ideal situation – rolling out a vaccine that hasn't been tested on pregnant people. "We're in a situation right now where we have to go forward with the information that we absolutely do not have. It's understandable that we don't have data from pregnant women yet, but it would be nicer if we did," she told NPR's Weekend Edition.

The American College of Obstetricians and Gynecologists, or ACOG, has urged the CDC's Advisory Committee on Immunization Practices not to exclude pregnant and lactating people from the high-priority populations for COVID-19 vaccine allocation. The group notes that pregnant people are at high risk from the coronavirus for multiple reasons: "In addition to being an identified at-risk group by themselves, upwards of half of pregnant women also fall into another priority category, including frontline workers and those with underlying conditions."

In Britain, regulators have advised against offering the Pfizer-BioNTech vaccine to pregnant people or those who are breastfeeding. They also warn that "women of childbearing age should be advised to avoid pregnancy for at least 2 months after their second dose."

Jamieson says that Canada's approach is better than the United Kingdom's. "The Pfizer instructions in Canada specify that pregnant women should talk to their health care provider," she says. "It's listed under one of the things that 'if you have this condition, discuss with your health care provider,' but they do not list it as a contraindication, and pregnant women are being vaccinated with the Pfizer vaccine in Canada."

What about breastfeeding?

In the U.S., the Society for Maternal-Fetal Medicine has stated that "there is no biological plausibility for the exclusion of lactating women from these trials."

"For some reason that does not make any sense to me, lactating and pregnant women are always lumped into one group," Jamieson says. "They're actually two very different groups, and there's even less theoretical reason to be concerned about lactating women. We give live viral vaccines — measles, mumps and rubella vaccine — routinely to lactating women. And that's a live viral vaccine."

Dr. Laura Riley, chair of the Department of Obstetrics and Gynecology at Weill Cornell Medicine and chair of ACOG's immunization committee, agrees.

"The thought that this mRNA vaccine is going to get into breast milk — really? We want to stop people from dying, and get the vaccine. I would hate to see a woman who is breastfeeding stop so that they could get the vaccine," Riley says.

Considerations for getting the vaccine while pregnant

Jamieson is hopeful, based on the public comments of the FDA, that the agency will do what ACOG has advocated: If a pregnant woman would otherwise be offered the opportunity to be vaccinated, she should talk to her health care provider and potentially be vaccinated.

The FDA could decide that pregnant people should not take the vaccine. But more likely, Faden says, it will be up to them and their doctors to decide what's best.

So assuming they get the option, how should pregnant people decide whether to get vaccinated for the coronavirus?

Faden recommends they assess their individual risk: their risk of becoming infected in the first place, and the risk of becoming seriously ill if infected with the virus.

"A disproportionate amount of burden of disease in pregnancy seems to be hitting women who are low-income, women who are from communities of color, women who are otherwise disadvantaged," she says. "There's nothing about pregnancy that is protective."

In consultation with a health care provider, Jamieson says, the pregnant person can then put that risk assessment together with what's known about mRNA vaccines, what's known about other vaccines during pregnancy and decide what makes sense.

Riley says she is getting flooded with calls from pregnant health care workers, asking what they should do: "I work in an ICU, I work in a COVID unit – should I get the vaccine?" they ask her.

"It's easy to say it's hand-wringing, but they're the front-line workers – whether they're a nurse, or a doc, or sitting at the front desk," Riley says. "I worry about the ladies at the grocery store every single day. At least if you're in a hospital, you've got PPE. But if you work in a grocery store, and you're riding the train to work — a lot of those people are pregnant or thinking of getting pregnant."

In the absence of vaccine trial data on pregnant people, the call on whether to get vaccinated will likely come down to that conversation between the pregnant person and the health care provider.

"People who are pregnant have a lot to worry about, and we don't need to add to people's stress," Faden says. "Unfortunately, this is a stressful circumstance. Take a deep breath, and if you're given the choice, it may make good sense to have this vaccine. It may not."

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