Preliminary study shows no need to cease breastfeeding following COVID-19 vaccination

By James DuckerReviewed by Emily Henderson, B.Sc.Jul 6 2021

A new study of 13 breastfeeding mothers has shown that components from the COVID-19 vaccine were not found in any breastmilk.

Woman Breastfeeding. Image Credit: SeventyFour/Shutterstock.com

First insights into breastfeeding post-vaccination for COVID-19

With the recent large-scale implementation of messenger RNA (mRNA) vaccines against COVID-19, clinical research has started to understand the dynamics of both the virus and the vaccine across demographic groups. Of particular importance are pregnant and breastfeeding mothers, from which clinical trials have limited data on the effects of vaccines for both mother and child.

Despite the recommendation of the World Health Organization (WHO) recommending that do not have to cease breastfeeding following vaccine administration, many mothers have ceased breastfeeding post-vaccination due to concern that maternal vaccination may alter human milk.

A new study from the University of California, San Francisco has revealed preliminary data of clinical trials showing mothers do not need to cease breastfeeding as components of the mRNA vaccine for COVID-19 were not found in any breastmilk samples.

The study, led by Dr. Yarden Golan from the Department of Bioengineering and Therapeutic Sciences at UoF, analyzed self-collected milk samples from 13 breastfeeding women before vaccination and at varied time points up to 48 hours after vaccination.

Then, researchers isolated total RNA from milk components using the RNeasy Mini Kit (Qiagen), before performing a real-time quantitative polymerase chain reaction (qPCR) assay targeting the mRNA used in the COVID-19 mRNA-based vaccines.

Vaccines considered included the BNT162b2(Pfizer) and mRNA-1273 (Moderna) vaccines, which were separately inoculated into pre-vaccination milk samples to use as positive control samples.

No vaccination components found in any breastmilk samples, but more data required

The analysis of the 13 samples collected 24 hours after vaccination that included samples 4 to 48 hours from a single participant, revealed that none of the samples showed detectable levels of vaccine mRNA in any component of the milk.

No detectable traces were found in any components, and authors confirm that if vaccines elements remained, the quantities would be so limited that the gastrointestinal tract of the children would be able to break them down.

Based on these preliminary findings, authors find no issues that may need for breastfeeding to be discontinued post-vaccination.

However, it is important to consider that the study was conducted on a limited sample size and only offers insights into individuals who received one type of vaccine. Further data could therefore be collected in the context of a larger study that includes a greater number of breastfeeding individuals from different vaccines over a larger time scale. The latter is a key factor, since despite vaccination concentration being highest immediately after vaccination, different vaccines may act differently over time.

Using a larger population for such a study could improve the reliability of findings to support the wider recommendation for breastfeeding mothers post-vaccination.