Vaccinated Mothers Are Trying to Give Babies Antibodies via Breast Milk

Multiple studies show that there are antibodies in a vaccinated mother’s milk. This has led some women to try to restart breastfeeding and others to share milk with friends’ children.,


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As soon as Courtney Lynn Koltes returned home from her first Covid-19 vaccine appointment, she pulled out a breast pump. She had quit breastfeeding her daughter about two months earlier because of a medication conflict. But she was off those pills, and she had recently stumbled across research suggesting that antibodies from a vaccinated mother could be passed to her baby through milk.

Getting the milk flowing again — a process known as relactation — would not be easy. She planned to pump on every odd-numbered hour from 7 a.m. to 11 p.m. But Ms. Koltes and her husband were eager to finally introduce their 4-month-old daughter to family members, and with children not yet eligible for vaccination, she was willing to try.

“I am starting to see very slow progress, so it is all worth it if it means I can protect her,” Ms. Koltes, who lives in Orange County, Calif., said last week — nine days after receiving her first dose of the Pfizer-BioNTech vaccine.

Partly because it’s so physically taxing, relactation is not common. (Medication is often also involved.) But over the past few weeks, online forums focused on relactation have been swarmed with newly vaccinated mothers like Ms. Koltes. Some had stopped breastfeeding their children more than a year earlier.

“I’m glad I’m not the only one here trying to relactate for this reason!” one woman wrote in a lively thread in a private Facebook group.

“Go team vaccine!” another wrote.

In stark contrast, other parenting and breastfeeding forums have been simmering with worries that breast milk from a newly vaccinated mother could be dangerous. It’s not only vaccine skeptics who have been encouraging those fears, which researchers say are unfounded: Some pediatricians and vaccine administrators have been urging nursing mothers to dump their milk after they are vaccinated.

So which is it? Is breast milk from a vaccinated person a sort of elixir capable of staving off Covid? And if so, are the newly vaccinated mothers sneaking breast milk into older children’s cereal or sharing their extra milk with friends’ babies onto something? Or should nursing mothers hold off on getting vaccinated?

The answer, six researchers agreed, is that newly vaccinated mothers are right to feel as if they have a new superpower. Multiple studies show that their antibodies generated after vaccination can, indeed, be passed through breast milk. As with so much to do with the coronavirus, more research would be beneficial. But there is no concrete reason for new mothers to hold off on getting vaccinated or to dump out their breast milk, they said.

ImageRebecca Powell, left, and her research team have collected breast milk samples for analysis at their Mount Sinai hospital lab.
Rebecca Powell, left, and her research team have collected breast milk samples for analysis at their Mount Sinai hospital lab.Credit…James Estrin/The New York Times

In the first nine months of the pandemic, around 116 million babies were born worldwide, according to Unicef estimates. This left researchers scrambling to answer a critical question: Could the virus be transmitted through breast milk? Some people assumed it could. But as several groups of researchers tested the milk, they found no traces of virus, only antibodies — suggesting that drinking the milk could protect babies from infection.

The next big question for breast milk researchers was whether the protective benefits of a Covid vaccine could be similarly passed to babies. None of the vaccine trials included pregnant or breastfeeding women, so researchers had to find lactating women who qualified for the first vaccine rollout.

Through a Facebook group, Rebecca Powell, a human milk immunologist at the Icahn School of Medicine at Mount Sinai in Manhattan, found hundreds of doctors and nurses willing to periodically share their breast milk. In her most recent study, which has not been formally published, she analyzed the milk of six women who had received the Pfizer-BioNTech vaccine and four who had received the Moderna vaccine, 14 days after the women had received their second shots. She found significant numbers of one particular antibody, called IgG, in all of them. Other researchers have had similar results.

“There is reason to be excited,” said Dr. Kathryn Gray, a maternal fetal medicine specialist at Brigham and Women’s Hospital in Boston, who has conducted similar studies. “We’d presume that could confer some level of protection.”

But how do we know for sure? One way to test this — exposing those babies to the virus — is, of course, unethical. Instead, some researchers have tried to answer the question by studying the antibodies’ properties. Are they neutralizing, meaning they prevent the virus from infecting human cells?

In a draft of a small study, one Israeli researcher found that they were. “Breast milk has the capacity to prevent viral dissemination and block the ability of the virus to infect host cells that will result in illness,” Yariv Wine, an applied immunologist at Tel Aviv University, wrote in an email.

Research is too premature for vaccinated mothers who are breastfeeding to act as if their babies can’t get infected, however, said Dr. Kirsi Jarvinen-Seppo, the chief of pediatric allergy and immunology at the University of Rochester Medical Center. Dr. Jarvinen-Seppo has been conducting similar studies. “There is no direct evidence that the Covid antibodies in breast milk are protecting the infant — only pieces of evidence suggesting that could be the case,” she said.

Destiny Burgess’s twins were born prematurely. Ms. Burgess and her husband are back at work in Asheville, N.C. One of their older children is in kindergarten. Two are in day care. All of that makes Ms. Burgess worried for her now 3-month-old babies.

When a vaccinated friend offered to share some of her milk with the twins, she accepted.

“I feel like I have this newfound superpower,” that friend, Olivia de Soria, said. Along with feeding her own 4-month-old and sneaking a bit of her milk into her 3-year-old’s chocolate milk, Ms. de Soria is now sharing her milk with five other families.

“They can’t get the shot, so this is giving me a little peace of mind,” said Ms. Burgess. She does wonder, though, how much “vaccinated milk” would be needed to make a dent.

The unsatisfying answer is that it’s not clear. What researchers agree on is that a baby who consumes breast milk all day long is more likely to be protected than one who gets just an occasional drop. But none scoffed at the idea of giving a bit to older children if it’s not a hassle.

They also agree that breast milk’s protective benefits work more like a pill that you must take every day than a shot that lasts a decade. This short-term defense — known as “passive protection” — may only last hours or days from the baby’s last “dose,” Dr. Powell said.

“It’s not the same as the baby getting vaccinated,” she added.

That means “as soon as you stop feeding that breast milk, there is no protection — period,” said Antti Seppo, another breast milk researcher at the University of Rochester Medical Center. Dr. Seppo also found that it took about two weeks after the first shot for the antibodies to show up in the milk and that they peaked after the second shot.

Multiple researchers involved in research on breast milk and the Covid vaccine offered slight variations of the same opinion. “There is no reason to think there is anything about this vaccine that would cause it to be harmful, and there’s reason to believe it would be beneficial,” said Christina Chambers, co-director of the Center for Better Beginnings at the University of California, San Diego.

So why are parenting forums brimming with anecdotes about pediatricians telling mothers to wait to get vaccinated until their baby is older or to dump their milk after vaccination? Mostly because lactating mothers were not included in vaccine trials, so researchers have not been able to concretely study risks.

But researchers’ confidence that breast milk from Covid-19-vaccinated mothers is safe comes from what is known broadly about how vaccines work.

“Unlike pregnancy, where there are theoretical safety concerns, there really aren’t concerns about lactation and vaccination,” said Dr. Kathryn Gray, a maternal fetal medicine specialist at Brigham and Women’s Hospital in Boston.

Both the Moderna and the Pfizer-BioNTech products are mRNA vaccines. “The ingredients in the vaccine are mRNA molecules that have a short lifetime and have no way of making their way into milk,” Dr. Seppo said.

Nearly two weeks in, Ms. Koltes of Orange County was managing to pump only a few drops of breast milk each session. An email exchange with her pediatrician reinforced that she could not be sure — even if she got the milk flowing — that allowing unmasked, unvaccinated relatives to hold her daughter was safe. She applauded other women having more success with relactation. But for her, that was it.

“It does feel like a weight is lifted,” she said of quitting her rigorous pumping schedule. Now all that’s left to do is wait for an actual vaccine for her daughter, she said. Both Pfizer and Moderna have recently begun testing their vaccines on babies as young as 6 months old.

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