Breast milk contains Covid genetic material but infected mothers will not pass virus through breastfeeding, study finds


Breastfeeding women infected with Covid-19 cannot transmit the virus through breast milk, according to a peer-reviewed study published in Pediatric research Tuesday, validating a small number of more limited studies and supporting recommendations from health organizations advising mothers to continue breastfeeding after infection and vaccination.


A small proportion of recently infected mothers had genetic material from the virus that causes Covid-19 in their breast milk – 6% of women with a positive test or symptomatic illness or 9% with just a positive test – according to researchers from the University of California, which analyzed samples from 110 women.

However, the researchers said there was “no evidence” that breast milk contained infectious virus or genetic material indicative of viral replication, noting that they were unable to grow the virus from the samples and that the genetic material was only “transiently present”.

There was also “no clinical evidence” to suggest infants became infected when breastfed by a mother with Covid-19, said lead author Paul Krogstad, suggesting that “breastfeeding does not is probably not a danger”.

The study is the largest of its kind to date and provides “substantial” support for a number of smaller studies with similar results, the researchers said, along with enhanced guidance from health organizations such as the Centers for Disease Control and Prevention and the World Health Organization. , which recommends that mothers continue to breastfeed during the pandemic.

Key Context

Breastfeeding has many benefits, but there are rare cases where breastmilk can transmit disease. This is a well-documented route of transmission for HIV and human T-cell lymphotropic virus – which can cause a type of leukemia and progressive nervous system disease – and Ebola virus has been detected in samples of breastmilk. The WHO says women with Covid-19 can breastfeed if they wish, but warns they should take precautions to avoid transmitting the infection by other means, including wearing a mask while breastfeeding. feeding, washing hands before and after touching the baby and regularly cleaning the surfaces they have touched.


Vaccination coverage for pregnant and breastfeeding women is well below average, fueled by confusing public health messaging that has changed as new information has come in and rampant misinformation baselessly suggesting that vaccines can somehow harm the mother, the child, or both (in fact, a Covid infection can have serious, life-threatening consequences for both). While some vaccines can transmit infection to breastfed infants — the CDC cites smallpox and yellow fever vaccines, both of which use live viruses — none of the widely used Covid-19 vaccines do. The vaccines themselves also do not appear in breast milk. The mother’s antibodies are passed into breast milk, providing some degree of protection against the virus.

Further reading

COVID vaccines and breastfeeding: what the data say (Nature)

No infectious SARS-CoV-2 in breast milk from a cohort of 110 breastfeeding women (Pediatric Research)

Vaccinated mothers try to give babies antibodies via breast milk (NYT)

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