Pregnant and Breastfeeding Women May Opt to Receive the Vaccine


In its emergency authorization of the Pfizer-BioNTech vaccine on Friday night, the Food and Drug Administration took an unexpected step, leaving open the possibility that pregnant and breastfeeding women may opt for immunization against the coronavirus.

The agency authorized the vaccine for anyone 16 and older, and asked Pfizer to file regular reports on the safety of the vaccine, including its use in pregnant women.

There had been no guarantee that the agency would take this route. The vaccine was not tested in pregnant women or in those who were breastfeeding. Regulators in the United Kingdom recommended against these women receiving the shots even while acknowledging that the evidence so far “raises no concerns for safety in pregnancy.”

The Centers for Disease Control and Prevention has not yet endorsed the vaccine for pregnant women, but an advisory committee to the agency is expected to meet this weekend to make further recommendations.

Some experts said the virus itself poses greater risks to pregnant women than the new vaccine, and noted that vaccines have been given to pregnant women for decades and have been overwhelmingly safe.

“This is a really huge step forward in recognizing women’s autonomy to make decisions about their own health care,” said Dr. Emily Miller, an obstetrician at Northwestern University and a member of the Covid-19 task force of the Society for Maternal and Fetal Medicine.

With the first doses of the vaccine reserved for health care workers and residents of long-term care facilities, the F.D.A.’s authorization most immediately affects the estimated 330,000 pregnant and breastfeeding health care workers in the United States.

“I am incredibly supportive of the F.D.A.’s decision to leave the door open to Covid vaccination for pregnant and lactating workers,” said Ruth Faden, a bioethicist at Johns Hopkins University in Baltimore.

Some health care workers are at high risk of Covid-19, either because their jobs bring them into intense contact with the virus — for example, cleaning the rooms of sick patients — or because they live in low-income and multigenerational homes, Dr. Faden said.

“We have to be able to give women the opportunity to think through this for themselves with whoever it is providing obstetrical care to them,” she said.

Health care organizations should also help their employees weigh the risks, and accommodate women who do not feel comfortable working on the front lines, she added.

None of the vaccine clinical trials have so far included pregnant or lactating women, nor even women who are planning to get pregnant; some trials are expected to begin in January.

Still, the American College of Obstetrics and Gynecology, the S.M.F.M. and other organizations have been calling on the F.D.A. to allow pregnant and lactating people access to the vaccine.

At a meeting on Thursday to review Pfizer’s data for an emergency use authorization, Dr. Doran Fink, the F.D.A.’s deputy director for vaccine development, signaled that the agency was open to the idea.

“We really have no data to speak to risks specific to the pregnant women or the fetus, but also no data that would warrant a contraindication to use in pregnancy at this time,” Dr. Fink said. “Under the E.U.A., they would be then free to make their own decision in conjunction with their health care provider.”

The E.U.A. did not endorse the vaccine for pregnant or breastfeeding women, other than to note that Pfizer should collect long-term data on how the vaccine performs in pregnant women.

Since the 1960s, pregnant women have been urged to receive vaccines against influenza and other diseases. These women are generally cautioned against live vaccines, which contain weakened pathogens.

Even so, the benefits of live vaccines outweigh the risks in some situations, said Dr. Denise Jamieson, an obstetrician at Emory University in Atlanta and a member of A.C.O.G.’s committee on Covid vaccines.

“We have a long track record of giving pregnant women vaccinations, and nearly all vaccinations are very safe,” Dr. Jamieson said.

Dr. Jamieson said she was “disappointed that F.D.A. was not more explicit” but encouraged that “there is no explicit contraindication regarding pregnancy, which is good.”

Health care providers should be prepared to counsel pregnant patients on the decision to be immunized, based on the patients’ potential exposures and underlying conditions like diabetes and obesity, Dr. Jamieson added.

“A woman who can stay home, who doesn’t have any other children and no one in the household is working, is very different than an essential worker who needs to go out every day and be around other people,” she said.

Women who are contemplating pregnancy should get both vaccine doses before trying to get pregnant, she added.

In the initial rollout, it will be mostly pregnant health care workers who must weigh the benefits and possible risks. By the time the vaccine is available to pregnant essential workers or to women in the general population, there should be a lot more data available, the experts said.

“The big question we don’t know quite yet is if it actually crosses the placenta,” said Dr. Geeta Swamy, an obstetrician at Duke University in Durham, N.C., and a member of A.C.O.G.’s Covid vaccine group, referring to the vaccine. “To be honest, what would be the most reassuring would be to see some of the animal data.”

So-called D.A.R.T. — developmental and reproductive toxicity — studies are conducted in animals to assess a vaccine’s possible effects on a fetus. These data are typically required for licensing a vaccine, but not for an E.U.A.

Animal studies would ideally have been conducted as soon as safety data on the vaccines were available and before companies started large trials, Dr. Faden, the bioethicist, said. But at the F.D.A. meeting on Thursday, officials at Pfizer hinted that the animal data would be available by the end of the year.

(Moderna did not respond to queries about its timeline for animal studies, and it was unclear whether AstraZeneca and Johnson & Johnson had begun theirs.)

“The vaccines that are behind — if they haven’t started their D.A.R.T. studies, they should start them yesterday,” Dr. Faden said.

The experts were particularly enthusiastic about the prospect that breastfeeding women might get the vaccine. “The biologic plausibility to there being some risk of harm to an infant from breastfeeding is extremely, extremely low,” Dr. Swamy said.

In the time it would take an antigen — the essential ingredient in the new vaccine — injected into a woman’s arm to travel through her bloodstream and into breast milk, the antigen would disintegrate.

“There’s not a good reason even to think that vaccinating children is unsafe,” Dr. Swamy added. “To be honest, the reason we don’t have pediatric studies yet is because they’re trying to figure out the right dosage.”

Some women breastfeed for years and, particularly in low- and middle-income countries, not being able to do so may have devastating consequences for babies, experts said.

“I would applaud the fact that the F.D.A. has recognized that in the absence of data and meaning in either direction, decisions should be made between patients and their providers,” Dr. Swamy said. “We’re talking about women who are adult individuals, right?”