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Here’s What Researchers Have Discovered So Far About COVID Vaccines And Donated Breast Milk

Organizations that provide donated breast milk to parents say fielding questions about how the vaccines figure into the transfer of antibodies has led to a “second layer of chaos” from the pandemic.

Posted on July 24, 2021, at 9:00 a.m. ET

Many small bottles of breast milk
Getty Images

Danielle Byrdsong loaded bags of breast milk into her car, preparing to make her first donation since receiving the Moderna COVID-19 vaccine in April.

“To be honest, I was a little concerned,” she said.

Byrdsong, a 36-year-old mother of two living in the Washington, DC, area, told BuzzFeed News that at the time, she didn’t know if getting the COVID vaccine would affect her ability to donate her breast milk — an information gap that is increasingly becoming a factor for milk banks as more of the US population is vaccinated. A key question from donors and recipients is whether protection against the coronavirus travels through a vaccinated person’s breast milk to an infant. While long-term studies at a larger scale are needed, early research suggests that the answer is yes.

“We don’t have that proof,” said Kim Updegrove, the executive director at Mothers' Milk Bank at Austin. “We are assuming that it's protective. We are assuming that it's coming through with the milk and that it's a really good thing. All of that leads to a very interesting question coming from people who sit on both sides of the vaccine fence.”

Fielding uncertainty about the vaccine has become the pandemic’s “second layer of chaos” for milk banks, Updegrove said. Fifteen months after the banks initially addressed panic over the effect COVID-19 might have on lactating or pregnant people, there is a growing need for information regarding whether infants are protected against the virus via the milk of vaccinated people.

Donations are typically collected by nonprofit organizations that test the milk, mix multiple donors’ milk into single batches, and distribute the nutrient-rich pooled product to medical providers for people like Paris Henderson, a 33-year-old mother whose son was born prematurely in May. The hospital offered her donor milk when her own milk didn’t come in after the early delivery; her body was behind schedule and unprepared to produce milk. Henderson hasn’t received a COVID-19 vaccine but tested positive for antibodies after she overcame the virus.

“I didn’t care if the person was vaccinated or not,” Henderson said about the people who donated the milk her son received. It mattered more to her that her baby received the nutrients in the milk, she added.

A main reason for confusion is a lack of robust clinical study about the effect of the COVID-19 vaccines on pregnant or lactating people. As is standard for most clinical trials, pregnant people were left out of the COVID-19 vaccine trials. To include them would have meant that researchers needed to collect data on both parents and babies, potentially prolonging the clinical trial process and raising complicated ethical questions. According to the CDC, there’s little to no information available about the safety and effects of the vaccines on breast milk as of now, but specific clinical trials are underway or planned.

“It just feels like another [instance] in which women are just sort of forgotten,” said Erin Burgin, a 35-year-old mother of two from the Washington, DC, area.

After becoming pregnant in 2020 and delivering a few months ago, Burgin said the lack of information on the safety of breastfeeding when vaccinated was “extremely unsettling.”

But that’s starting to change.

A recent joint study from Brigham and Women’s Hospital and Massachusetts General Hospital concluded that vaccinated parents do in fact pass their antibodies to infants via their breast milk. The study took place from December 2020 to February 2021 and evaluated 131 women who were either of reproductive age, lactating, or pregnant and about to receive either the Pfizer or Moderna shots. The researchers had two goals in mind: track if their vaccines worked against COVID-19 and, if so, whether the shot also provided protection to infants.

A gloved worker guides breast milk from a dropper into a test tube
Mothers' Milk Bank at Austin

Donor breast milk at the Mothers' Milk Bank at Austin is pasteurized and pooled into a single product.

“We found that, reassuringly, pregnant and lactating women made similar amounts of antibodies in response to the vaccination, so vaccination was effective,” Dr. Kathryn Gray, lead author of the study, told BuzzFeed News. “For all the lactating individuals in our study, we found that the maternal antibodies also crossed into the breast milk. That suggests that there may be some benefit and protection conferred to infants from pregnant individuals and lactating individuals who are vaccinated.”

But the immunity benefits for the baby don’t last long after weaning, Stephanie Gaw, an assistant professor of obstetrics, gynecology, and reproductive sciences at the University of California, San Francisco, told BuzzFeed News. The antibodies coat the baby’s mouth, throat, and digestive tract, keeping the virus from infecting the baby’s cells, but researchers don’t know for how long.

Gaw led a small study that determined both the Moderna and Pfizer vaccines do not cross into breast milk. The study analyzed the breast milk of seven individuals at various time points after they received either mRNA vaccine. Researchers said the results bolstered recommendations that lactating people who get the vaccine shouldn’t stop breastfeeding. Gaw added that she saw no harm in mixing pre- and post-vaccine milk.

While the new findings are reassuring, the results shouldn’t change how milk banks pool their donations, both Gaw and Gray said. Gray emphasized that prior to the pandemic, adults who produce breast milk are typically exposed to myriad infections and receive vaccines frequently.

And as the population becomes more immune to COVID-19, these antibodies will just become another layer of protection breast milk provides babies that formula doesn’t. But consistency is important, a report in Nature found, because babies process antibodies within a matter of hours or days. As a result, any layer of protection that breast milk provides lasts only as long as babies are breastfed.

“We have always asked about vaccinations during our screening process, so this is just a new set of information for us to collect,” said Rebecca Heinrich, director of Mothers’ Milk Bank. “We do not yet know what sort of antibody ‘load’ is transferred, or what sort of immune system boost it might provide, but of course our hope is that antibodies in donor milk help protect the infant from all sorts of pathogens, including COVID-19.”

Byrdsong, the mother of two living in DC, said that for people like her, the first step should be clearing up confusion over whether antibodies or the vaccine itself is transferred via breast milk.

“I think that most mothers who have concerns about the vaccine ... their discomfort with it has to do with the vaccine itself being given directly to a child versus antibodies,” Byrdsong said. “Personally, I don't know any mother who is against their child receiving antibodies, so I don't know if that's something that they understand, that there's a difference between the two.”

Burgin, who received the Moderna vaccine this spring, said she is currently breastfeeding her 6-month-old baby and gives her 3-year-old child a glass of breast milk each week as an immunity boost. Gaw said it’s not yet clear how much milk an older child would need to achieve immunity or how long that immunity would take.

“I talked to other moms who said that they've continued their breastfeeding journey longer because they had the vaccine and they want to help some of their older kids in their house,” Burgin said. “It's a huge discussion … and breast milk is an easy way to give [protection] to your kid who can't get the vaccine yet.”

Milk banks typically ask donors if they’ve received other major vaccines, such as against the measles, but they don’t yet have a standardized method to prove that they’ve gotten the COVID-19 vaccine or if they have responded positively and developed antibodies, Updegrove said. However, on average, more than 50% of donors in most states have self-reported in their profile that they received one of the FDA-approved vaccines, she added.

Colorful bins of bottled breast milk
Mothers' Milk Bank at Austin

The Mothers' Milk Bank at Austin estimates it will process about 900,000 ounces of donor breast milk in 2021, about 100,000 more ounces than last year.

But that won’t change the way donated milk is pasteurized, said Lindsay Groff, executive director for Human Milk Banking Association of North America. She added that so far, there’s no information about the vaccine's effect on breast milk that would make any changes to the donation process necessary.

Experts are also reminding parents that since milk from banks is pooled from multiple people, it’s not possible to request milk from unvaccinated donors unless the recipient seeks it directly from an individual.

“The reason why multi-donors are recommended in one pool of milk is that the women who are lactating and expressing their milk are not the same,” Updegrove said. “They're eating different diets, they're taking different vitamins. There's a value in mixing multiple different donors.”

When asked about the typical profile of breast milk donors, Grey said she hopes to diversify the research on the vaccine’s effect on people who are lactating, since her study consisted primarily of white, non-Latino women.

Henderson said important information about the health and immunity benefits of breast milk has been lacking among Black parents, and in her case, where she lives in Vienna, Virginia, determined her ability to receive a donation.

“I think more women in my community in particular would breastfeed if they knew that they were providing their child with a sense of protection,” Henderson said. “I don't think that the information is there. Lactation consultations and breastfeeding centers, they're not available to all. We were fortunate to have our hospital in a wealthier area. That's why we got the donor milk … and they said, ‘This is not something that’s offered everywhere.’ We may not have been fortunate enough to have it.”

Now that her milk supply has come in, Henderson said she would “absolutely” donate her milk.

“You could be saving somebody's life or preventing a baby from getting sick,” she said. “They're so susceptible to everything anyways, just that one little layer of protection. You don’t really know, but I feel like it gives a parent peace of mind. A sense of comfort. And that's what I go back to. I don't know that I'm doing everything, but I know that at least I'm trying.”

A BuzzFeed News investigation, in partnership with the International Consortium of Investigative Journalists, based on thousands of documents the government didn't want you to see.