Study: Virus not passed through breast milk

There is no risk that COVID-19 can be passed to babies through their mother’s breast milk, and infected mothers may provide some protection to nursing infants against the disease according to new research led by University of Idaho scientists.

UI professor Michelle McGuire, who helped lead the study, described the phenomenon as the mother “educating the baby how to best survive in this environment through her milk.”

“We’ve identified specific antibodies in the milk that not only binds to the virus, but kills the virus … these are her antibodies and she’s putting them into the milk for her baby” McGuire said. “It’s a really quick response, these moms are producing what we call ‘neutralizing antibodies,’ — they’re very specific to killing SARS-CoV-2.”

McGuire, who also directs the UI School of Family and Consumer Sciences, said newborns’ immune systems are immature so mothers commonly pass on immune components through nursing.

In the case of the novel coronavirus, she said the effect is roughly analogous to immune-boosting therapies that use antibody-rich blood plasma donated by people who have recovered from an infection.

The initial study, funded by the Bill and Melinda Gates Foundation, examines milk samples from 18 different women for traces of the virus. More than 60 infected women participated in the research overall. She said a second paper analyzing more than 300 milk samples is forthcoming and will support those initial findings.

McGuire said some early, albeit flawed, studies appeared to indicate the virus could be transmissible through nursing, causing a global panic. She said she believed milk samples in these early studies may have been contaminated by viral material that was present on the surface of the donor’s breast.

“We wanted to answer that question by taking a swab of the breast, and then cleaning the breast and then taking another swab, and then taking the milk sample,” McGuire said. “Interestingly, we found the virus on about 20 percent of those pre-cleaning breast swabs — which I think probably explains why some groups have found evidence of the virus in the milk. I think it’s contamination from the breast.”

While the question of whether a virus can be transmitted through breastfeeding is incredibly consequential to the global community, McGuire said it was not high-priority research at the onset of the pandemic.

She said while the U.S. Centers for Disease Control and Prevention and their peer institutions around the globe were researching elemental questions about the virus, little data was gathered about its transmissibility through nursing.

She said other diseases like HIV, ebola and tuberculosis can be transmitted via breastfeeding and the global health community worried COVID-19 would behave similarly. Because of this ambiguity, she said hospitals around the world were separating mothers from their infants and advising them to avoid breastfeeding. She said this is a particularly difficult recommendation to follow in parts of the world where breastmilk alternatives are not widely and readily available.

She said this lack of attention to the information needs of pregnant women resulted in an additional crisis — vaccines were not tested on pregnant women. Even though many agencies have since said pregnant women can be safely inoculated against COVID-19, she noted many countries are still not allowing them to be vaccinated.

McGuire said she hopes this serves as a “call to action” for health organizations around the world that questions surrounding the safety of breast milk are incredibly consequential during a global health crisis and a lack of information can result in real harm.

“There are women breastfeeding and having babies … every day, this is not a minor question and it’s going to happen every single pandemic,” McGuire said. “We’ve screwed up the last how many pandemics because this is an afterthought for the global health community, which is ridiculous.”

Scott Jackson can be reached at (208) 883-4636, or by email to sjackson@dnews.com.