I spend a lot of time discussing wild claims about the COVID-19 mRNA vaccine, most of which are just patently false. However, there is some research that shows that the messenger RNA (mRNA) that is encapsulated in the lipid nanoparticles, the method to deliver the mRNA fragment to the cell, can be found in tiny quantities in the breast milk of women who have been recently vaccinated.

Initially, when vaccines were deployed with mRNA encapsulated in lipid nanoparticles (LNPs), researchers thought it remained near the injection site and quickly degraded. But now it appears that some mRNA in LNPs do travel in the bloodstream and go to other sites. There are no safety concerns about this, the mRNA is delivered to cells outside of the injection site to induce cells to produce the spike protein which, in turn, causes an immune response.

A new study evaluated whether breast milk contained these mRNA lip nanoparticles after receiving a COVID-19 vaccine. Also, the researchers explained that there was probably no safety issue from it.

As I usually do, we will take a look at the newly published research on the COVID-19 mRNA vaccine and breast milk.

COVID-19 vaccine mRNA in breast milk

In a study published on 19 September 2023 in Ebiomedicine, Nazeeh Hanna, MD, New York University Grossman Long Island School of Medicine, and colleagues examined the expressed breast milk (EBM) of 13 lactating women who had recently received an mRNA-based COVID-19 vaccine. This was an update of the group’s research on the same issue published on 1 December 2022 in JAMA Pediatrics.

Of these 13 women, 10 had trace mRNA amounts detected in their EBM for up to 48 hours post-vaccination.

However, just observing trace mRNA amounts has very little meaning to the safety of the vaccine. First, according to recent research, the amount of mRNA vaccine detected in the EBM is of little concern because it is less than 0.002% of the dose found at the intramuscular vaccine site.

Second, if the mRNA particle is swallowed by the baby through breast milk, it is highly unlikely that it would induce any kind of response. The mRNA will be broken down in the gut into simple nucleic acids that are similar to all other nucleic acids found in the gut of all human beings after consuming food. All food (whether animal or vegetable) contains mRNA which will be broken down into these nucleic acids which are then absorbed and used by the body to create new mRNA.

These researchers speculated that, following the vaccine administration, lipid nanoparticles containing the vaccine mRNA are carried to mammary glands via hematogenous and/or lymphatic routes.

Of course, we do not have enough research to know if this mRNA dose could elicit an immune reaction in these infants. The CDC’s Interim Clinical Considerations of not recommending mRNA vaccine exposure in infants <6 months of age because of the lack of safety studies and until vaccine exposure risks are clinically evaluated.

The new study’s researchers concluded:

Our findings suggest vaccine mRNA spreads systemically and can be packaged into EBM. This research should prompt a discussion among the experts responsible for formulating policies related to breastfeeding after mRNA vaccination, as information transparency is imperative as the risk/benefit balance of any vaccine can change over time.

Although we believe breastfeeding after mRNA vaccination is safe, a dialogue between a breastfeeding mother and her healthcare provider should address the benefit/risk considerations of breastfeeding in the first two days after maternal mRNA vaccination.

Summary

There is no evidence that the mRNA-based COVID-19 vaccine being expressed in breast milk has any safety issues for the child. However, there is also no research showing that it is safe, though most of these studies make the same statements — the amount in breast milk is tiny and it is probably safe.

For those mothers who might be concerned and want to be vaccinated against COVID-19, the protein subunit vaccines from Novavax do not use the mRNA fragment and might relieve any worry.

I am not concerned about this, because the mRNA fragment doesn’t do anything but induce cells to produce the spike protein which causes the immunity to COVID-19. I know that a lot of people make all kinds of wild claims about mRNA vaccines but they are almost all false.

Citations

• Hanna N, Heffes-Doon A, Lin X, Manzano De Mejia C, Botros B, Gurzenda E, Nayak A. Detection of Messenger RNA COVID-19 Vaccines in Human Breast Milk. JAMA Pediatr. 2022 Dec 1;176(12):1268-1270. doi: 10.1001/jamapediatrics.2022.3581. Erratum in: JAMA Pediatr. 2022 Nov 1;176(11):1154. PMID: 36156636; PMCID: PMC9513706.
• Hanna N, De Mejia CM, Heffes-Doon A, Lin X, Botros B, Gurzenda E, Clauss-Pascarelli C, Nayak A. Biodistribution of mRNA COVID-19 vaccines in human breast milk. EBioMedicine. 2023 Sep 19;96:104800. doi: 10.1016/j.ebiom.2023.104800. Epub ahead of print. PMID: 37734205; PMCID: PMC10514401.
• Low JM, Gu Y, Ng MSF, Amin Z, Lee LY, Ng YPM, Shunmuganathan BD, Niu Y, Gupta R, Tambyah PA, MacAry PA, Wang LW, Zhong Y. Codominant IgG and IgA expression with minimal vaccine mRNA in milk of BNT162b2 vaccinees. NPJ Vaccines. 2021 Aug 19;6(1):105. doi: 10.1038/s41541-021-00370-z. PMID: 34413319; PMCID: PMC8376902.