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UCSD Study: COVID-19 Unlikely To Pass Through Breast Milk

A bag of frozen breast milk in this file photo taken June 17, 2015.
Matt Rourke / AP
A bag of frozen breast milk in this file photo taken June 17, 2015.

A newly released study conducted by UC San Diego and UCLA researchers found it is unlikely that COVID-19 can be passed to infants through breast milk.

The researchers from UCSD's School of Medicine and UCLA collaborated to examine 64 samples of breast milk collected by the Mommy's Milk Human Milk Research Biorepository from 18 women across the United States infected with severe acute respiratory syndrome coronavirus 2, also known as SARS-CoV-2.

Although one sample tested positive for viral RNA, subsequent tests found that the virus was unable to replicate, and thus unable to cause infection in the breastfed infant.


According to a UCSD statement, there have been no documented cases to date of an infant contracting COVID-19 as a result of consuming infected breast milk.

"Detection of viral RNA does not equate to infection. It has to grow and multiply in order to be infectious and we did not find that in any of our samples," said study co-principal investigator Christina Chambers, a professor of pediatrics at UCSD School of Medicine and director of the biorepository. "Our findings suggest breast milk itself is not likely a source of infection for the infant.

"This is a very positive finding for donor milk, which so many infants, especially those born premature, rely on," Chambers said. "Our findings fill in some important gaps, but more studies are needed with larger sample sizes to confirm these findings."

The study, published Wednesday in the online edition of JAMA: The Journal of the American Medical Association, recommends hand hygiene and sterilizing pumping equipment after each use to prevent transmission while breastfeeding.

"In the absence of data, some women infected with SARS-CoV-2 have chosen to just not breastfeed at all," said Dr. Grace Aldrovandi, co-principal investigator of the study and a professor of pediatrics in the David Geffen School of Medicine at UCLA.


"We hope our results and future studies will give women the reassurance needed for them to breastfeed," she said. "Human milk provides invaluable benefits to mom and baby."

Early breastfeeding is associated with a reduced risk of sudden infant death syndrome and obesity in children, as well as improved immune health and performance on intelligence tests. In mothers, breastfeeding has been associated with lower risks for breast and ovarian cancer, cardiovascular disease and type 2 diabetes.

Chambers said additional research will not only look at whether breast milk is free of the virus, but also whether it contains active antiviral components. Further study is needed on antibodies to SARS-CoV-2 that women may produce after exposure to the virus and then transfer to their infants through breast milk, protecting them from COVID-19.