“Studies that have looked at the health of breastfed babies shortly after their mothers have been vaccinated have also found no problems,” she continued. “Taken together, this body of evidence suggests that there should be no problem with breastfeeding shortly after you have been vaccinated.”
She added that the Royal College of Obstetricians and Gynaecologists in the U.K. says that women should not stop breastfeeding to get vaccinated against COVID-19. This is similar to what ACOG, the American Academy of Pediatrics, the Academy of Breastfeeding Medicine and the WHO all say.
“Breastfeeding after vaccination is safe for the baby,” ACOG explains in an FAQ. “There is no need to stop breastfeeding if you want to get a vaccine. When you get vaccinated, the antibodies made by your body may be passed through breast milk and may help protect your child from the virus.”
The lead author, neonatologist Dr. Nazeeh Hanna, defended the inclusion of the “caution is warranted” line in his paper in an interview with us, but explained that what this meant was that if mothers had any concerns about the mRNA in milk, they could “pump and dump” for the 48 hours after a vaccination. He was not suggesting that lactating mothers not get vaccinated.
Pumping and dumping refers to expressing breast milk, usually with a breast pump machine, and then discarding that milk. Hanna suggested that mothers who opt for this approach pump extra milk before vaccination to feed their babies for the two days that they would be throwing out milk, rather than using formula.
“If you want to be on the safe side, and be more cautious … don’t expose the babies for now, because there could be some concern — could be,” he said.
The rationale for the caution, Hanna said, applied to babies 6 months and younger, since vaccines have not been tested or authorized in younger children. He said he didn’t think the trace mRNA would harm babies — and in theory, it could be good — but because it’s unknown, people should be informed about the temporary presence of the mRNA in breast milk.
But other experts do not think there’s enough of a possibility of harm to warrant such caution.
Study Results Not Concerning, Experts Say
“There is absolutely no justification to withhold breastmilk after getting the vaccine, even with the detection of trace amounts of mRNA. There is mRNA from many sources in breastmilk, which is not dangerous and also unlikely to survive the digestive tract of the baby anyways,” Dr. Stephanie Gaw, a maternal-fetal medicine physician scientist at the University of California, San Francisco, told us in an email.
“The clinical or biological significance of these trace amounts is not studied, and most scientist[s] would consider it not clinically relevant,” she continued. “Suggesting that mothers pump and dump is reckless and potentially harmful to the mother and baby (withholds safe nutrition from the baby, disrupts the breastfeeding relationship, and imposes stress on the days) with absolutely no justification.”
Gaw was senior author on an earlier JAMA Pediatrics paper that did not use special methods to increase the ability to detect trace amounts of mRNA, and found no vaccine mRNA in breast milk samples from seven mothers. She also authored a study of 50 pairs of lactating mothers and babies, which failed to find any evidence that polyethylene glycol, one of the lipids in the vaccines that protects the mRNA, made it into milk. That study also did not observe any severe side effects in mothers or their infants.
It’s worth noting that the amount of mRNA detected in breast milk is nowhere near the amount in a vaccine. Even at the highest detected concentration of mRNA in the JAMA Pediatrics paper, a baby would have to consume 256 liters of breast milk to reach the 3 microgram amount in a single vaccine dose of the Pfizer/BioNTech vaccine, which is authorized for children as young as 6 months. Babies consume at most a bit more than a liter of breast milk a day.
(For this reason, even if in theory mRNA transfer in breast milk could be good for infants, it’s difficult to imagine how they would get enough to see any effect. The possible benefits of vaccination via breast milk would be due to the transfer of protective antibodies or immune cells — not through mRNA.)
Male, of Imperial College London, was not necessarily against “pumping and dumping,” but also said that stopping breastfeeding, even for a short time, is “not without harms of its own, particularly for people who are not used to expressing milk, and babies who are not used to taking bottles. It’s important for people to fully consider these issues, with support from their doctor or midwife if necessary.”
Both Gaw and Male noted that having mRNA in breast milk is normal, and people ingest and digest mRNA all the time from food and the environment. Hanna said that the mRNA in extracellular vesicles in breast milk would survive digestion, and could be absorbed by the gastrointestinal tract. A few studies have found that some breast milk vesicles carrying proteins or microRNAs (a different RNA from mRNA) can survive digestion.
But as virologist Angela Rasmussen of the University of Saskatchewan told us, the JAMA Pediatrics study didn’t assess whether the vesicles with vaccine mRNA were able to survive digestion. Even if they did, she said, “the quantities of mRNA are so minute, they will have no biological impact.”
“Furthermore,” she added, “given that thousands—maybe millions—of lactating people have been vaccinated and there is no indication whatsoever that this has any observable clinical impact on nursing infants, I’d be a lot more ‘cautious’ about putting my infant at risk of getting COVID by not getting vaccinated or boosted.”
Editor’s note: SciCheck’s COVID-19/Vaccination Project is made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. The goal of the project is to increase exposure to accurate information about COVID-19 and vaccines, while decreasing the impact of misinformation.
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