A new study published in JAMA Pediatrics has clearly demonstrated that, contrary to prior assertions on the part of pharmaceutical companies and governmental authorities, mRNA from the COVID vaccine (both Pfizer and Moderna) does pass into human breast milk if the mother is vaccinated.

When the COVID vaccines were first rolled out amost two years ago, health authorities across the world insisted that the mRNA that was injected into the shoulder muscle remained in that muscle and that if it did escape the deltoid area, it would be drained via the local lymph nodes. Scientists have long disputed this assertion, given that Pfizer's own biodistribution studies in animals showed lipid nanoparticles spreading throughout the body and collecting in various organs including the reproductive organs.

Unfortunately, the biodistribution studies were halted at 48 hours post vaccination and the rats killed, making it impossible to know whether the effect was short-lived or persisting. However, later studies have shown mRNA to persist in the human body following vaccination for weeks, which was admitted by the Centers for Disease Control and Prevention (CDC).

This latest study examined the breast milk of 11 lactating mothers and found lipid nanoparticles from COVID vaccines in the milk of seven of them. The particles were detected only in the first 48 hours following vaccination, according to the researchers.

The study's authors noted the relatively small sample size as a limitation of the study. All the same, a prior study conducted in 2021 based on just 13 women was deemed sufficient by Reuters to declare breastmilk mRNA-free.

The present study's authors also noted that they did not test the possible cumulative effect of vaccine mRNA exposure in infants who breastfeed frequently.

"We believe it is safe to breastfeed after maternal COVID-19 vaccination," they conclude. "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. 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. It is critical that lactating individuals be included in future vaccination trials to better evaluate the effect of mRNA vaccines on lactation outcomes."