Breast milk is not likely to transmit COVID-19, according to a study which found that the novel coronavirus was unable to replicate and cause infection in the breastfed infants. The study, published on Wednesday in the journal JAMA, examined 64 samples of breast milk collected by a biorepository from 18 women across the US infected with severe acute respiratory syndrome coronavirus 2 (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 infants, the researchers said. "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 Christina Chambers, co-principal investigator of the study, and a professor at the University of California (UC) San Diego School of Medicine.
"Our findings suggest breast milk itself is not likely a source of infection for the infant," Chambers said. The current recommendations to prevent transmission while breastfeeding are hand hygiene and sterilizing pumping equipment after each use.
"In the absence of data, some women infected with SARS-CoV-2 have chosen to just not breastfeed at all," said Grace Aldrovandi from UC Los Angeles. "We hope our results and future studies will give women the reassurance needed for them to breastfeed. Human milk provides invaluable benefits to mom and baby," Aldrovandi said.
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, the researchers said. In mothers, breastfeeding has been associated with lower risks for breast and ovarian cancer, cardiovascular disease and type 2 diabetes, they said.
The researchers also mimicked conditions of the Holder pasteurisation process commonly used in human donor milk banks by adding SARS-CoV-2 to breast milk samples from two different donors who were not infected. The samples were heated to 62.5 degrees Celsius for 30 minutes and then cooled to 4 degrees Celsius.
Following pasteurisation, infectious virus was not detected in either sample. "This is a very positive finding for donor milk, which so many infants, especially those born premature, rely on," said Chambers.
"Our findings fill in some important gaps, but more studies are needed with larger sample sizes to confirm these findings," she said.