Scientists at New York University’s Long Island School of Medicine have detected messenger RNA COVID-19 vaccines in human breast milk, according to a new study.
This peer-reviewed research, published on September 26, 2022 in the journal JAMA Pediatrics, looked at the breastmilk of 11 healthy breastfeeding women, five of whom had received the Moderna vaccine during pregnancy and six of whom received the Pfizer vaccine.
Participants in the study were asked to collect and freeze their milk before and after vaccination. The milk collected before vaccination served as the control.
One hundred and thirty-one breast milk samples were collected between one hour and five days after women received the vaccines. Just under half of the women enrolled in the study (five out of 11) had detectable amounts of mRNA vaccine components in their breastmilk.
However, no mRNA vaccine was found in the pre-vaccine samples or in the samples taken 48 hours or more after vaccination.
The scientists speculated that after vaccination, lipid nanoparticles containing vaccine mRNA are carried to the mammary glands either through the blood or the lymphatic system.
The study authors contended that they were the first to report that vaccine mRNA reaches breast tissue. Their work seems to have hit a nerve: In the two weeks that this study has been available on-line, it’s been viewed well over 150,000 times, which is highly unusual for a scientific research letter about breastfeeding.
At the same time, the scientists claimed in their study that it proved that vaccinating breastfeeding women is safe. “The sporadic presences of trace quantities of COVID-19 vaccine mRNA detected … suggest that breastfeeding after COVID-19 mRNA vaccination is safe, particularly beyond 48 hours after vaccination,” they concluded.
NYU Scientists Urge Caution
While they did say they believed it was safe for vaccinated mothers to breastfeed, the researchers did add a cautionary note in their discussion.
“However, caution is warranted about breastfeeding children younger than 6 months in the first 48 hours after maternal vaccination, until more safety studies are conducted,” they wrote. “In addition, the potential interference of COVID-19 vaccine mRNA with the immune response to multiple routine vaccines given to infants during the first 6 months of age needs to be considered.”
As the researchers pointed out, initial vaccine safety trials excluded several groups of people, including babies, small children, pregnant women, and lactating moms. However, the CDC is now recommending mRNA vaccines for all of these groups except for infants under six months old.
