In the first nine months of the pandemic, Unicef estimates that around 116 million babies were born worldwide. This led researchers to scramble to answer a critical question: could the virus be transmitted through breast milk? Some people assumed it was possible. When several research groups tested the milk, they found no traces of viruses, only antibodies – suggesting that drinking the milk might protect babies from infection.
The next big question for breast milk researchers was whether the protective benefits of a Covid vaccine could similarly be transferred to babies. None of the vaccine studies included pregnant or breastfeeding women, so researchers had to find breastfeeding women who qualified for the first vaccine launch.
Through a Facebook group, Rebecca Powell, a breast milk immunologist at the Icahn School of Medicine on Mount Sinai in Manhattan, found hundreds of doctors and nurses willing to share their breast milk on a regular basis. In her most recent study, which was not officially published, she analyzed the milk of six women who received the Pfizer BioNTech vaccine and four women who received the Moderna vaccine 14 days after the women received their second shots had. She found a significant number of a specific antibody, called IgG, in all of them. Other researchers have found similar results.
"There is cause for concern," said Dr. Kathryn Gray, a maternal fetal medicine specialist at Brigham and Women's Hospital in Boston, has done similar studies. "We assume that this could offer some level of protection."
April 8, 2021, 9:44 p.m. ET
But how do we know for sure? One way to test this – exposing these babies to the virus – is, of course, unethical. Instead, some researchers have tried to answer the question by studying the properties of the antibodies. Do they neutralize, which means they prevent the virus from infecting human cells?
In a draft small study, an Israeli researcher found that this was the case. "Breast milk has the ability to prevent the spread of viruses and block the virus' ability to infect host cells that lead to disease," wrote Yariv Wine, an applied immunologist at Tel Aviv University, in an email.
The research is too premature for vaccinated mothers who are breastfeeding to pretend their babies can't become infected, said Dr. Kirsi Jarvinen-Seppo, Senior Consultant Pediatric Allergy and Immunology, University of Rochester Medical Center. Dr. Jarvinen-Seppo has carried out similar studies. "There is no direct evidence that the Covid antibodies in breast milk are protecting the child – only evidence that suggests it might," she said.