Vaccine mRNA not found in breast milk after COVID mRNA vaccination

A study conducted by researchers in the United States has found no evidence to suggest that the messenger RNA (mRNA) present in the Pfizer-BioNTech and Moderna vaccines that protect against coronavirus disease 2019 (COVID-19) can be transferred to human breast milk.

The team’s analysis did not detect any vaccine-related mRNA in breast milk samples collected from six individuals up to 48 hours after being immunized with one of the vaccines.

Stephanie Gaw and colleagues from the University of California in San Francisco say the findings support recommendations from the World Health Organization (WHO) and the Academy of Breastfeeding Medicine (ABM) that lactating individuals who receive an mRNA-based vaccine should continue to breastfeed their infants uninterrupted.

However, clinical data from larger populations is needed to better estimate the effect of these vaccines on lactation outcomes, adds the team.

A pre-print version of the research paper is available on the medRxiv* server, while the article undergoes peer review.

Study: COVID-19 mRNA vaccine is not detected in human milk. Image Credit: myboys.me / Shutterstock
Study: COVID-19 mRNA vaccine is not detected in human milk. Image Credit: myboys.me / Shutterstock

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

Rollout of the mRNA-based vaccines has started in several countries

Several countries have begun to rollout mRNA-based COVID-19 vaccines that have recently been approved for emergency use.

The mRNA in these vaccines codes for a protein called “spike,” found on the surface of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the agent that causes COVID-19.

This spike is the main structure the virus uses to infect host cells and a major target of the neutralizing antibodies that are generated following vaccination.

However, phase 3 clinical trials of the Pfizer-BioNTech and Moderna vaccines currently being rolled out did not include pregnant or lactating women, despite an increased risk of severe COVID-19 complications in this population group.

Consequently, no clinical data are available regarding the safety or efficacy of mRNA-based vaccines in this population.

The WHO advises that breastfeeding individuals accept a vaccine if they belong to a prioritized group such as healthcare workers and continue to breastfeed after receiving the vaccine. The ABM also states that there is little plausible risk that vaccine lipid particles would enter the bloodstream and breast tissue or that nanoparticles or mRNA would be transferred to breast milk.

However, some mothers have still chosen to decline vaccination, while others have opted to “pump and dump” breast milk for up to 72 hours post-vaccination, and some have stopped breastfeeding altogether.

What did the current study involve?

Human breast milk samples were collected from six individuals between 4 and 48 hours following vaccination with either the Pfizer-BioNTech BNT162b2 vaccine (n=5) or Moderna’s mRNA-1273 vaccine (n=1).

Total RNA was isolated from breast milk components, including cells, the supernatant and the fat layer.

The gold standard method of SARS-CoV-2 detection – reverse transcription-quantitative polymerase chain reaction (RT-qPCR) – was performed in triplicate using primers that specifically target the vaccines’ spike-coding mRNA.

The Moderna vaccine was “spiked into” pre-vaccine samples before RNA extraction to provide a positive control. Pre-vaccine samples that did not have the vaccine added served as negative controls.

What did the team find?

The researchers detected vaccine mRNA in the “spiked-in” pre-vaccine samples, with higher levels detected in the fat layer fraction.

However, milk samples collected from six individuals within 24 hours of vaccination and six serial milk samples collected at 4, 8, 22, 28, 33, and 48 hours post-vaccination showed no evidence of vaccine-related mRNA in any of the breast milk components tested.

What did the authors conclude?

“We show here that the mRNA from anti-COVID vaccines is not detected in human breast milk samples collected 4-48 hours post-vaccine,” says Gaw and colleagues.

The researchers say the findings support recommendations from the WHO and ABM that lactating women who receive an mRNA-based vaccine continue to breastfeed their infants uninterrupted.

However, “clinical data from larger populations need to be collected and analyzed to better estimate the effect of these vaccines on lactation outcomes,” advises the team.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

Journal references:

Article Revisions

  • Apr 7 2023 - The preprint preliminary research paper that this article was based upon was accepted for publication in a peer-reviewed Scientific Journal. This article was edited accordingly to include a link to the final peer-reviewed paper, now shown in the sources section.
Sally Robertson

Written by

Sally Robertson

Sally first developed an interest in medical communications when she took on the role of Journal Development Editor for BioMed Central (BMC), after having graduated with a degree in biomedical science from Greenwich University.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Robertson, Sally. (2023, April 07). Vaccine mRNA not found in breast milk after COVID mRNA vaccination. News-Medical. Retrieved on July 16, 2024 from https://www.news-medical.net/news/20210309/Vaccine-mRNA-not-found-in-breast-milk-after-COVID-mRNA-vaccination.aspx.

  • MLA

    Robertson, Sally. "Vaccine mRNA not found in breast milk after COVID mRNA vaccination". News-Medical. 16 July 2024. <https://www.news-medical.net/news/20210309/Vaccine-mRNA-not-found-in-breast-milk-after-COVID-mRNA-vaccination.aspx>.

  • Chicago

    Robertson, Sally. "Vaccine mRNA not found in breast milk after COVID mRNA vaccination". News-Medical. https://www.news-medical.net/news/20210309/Vaccine-mRNA-not-found-in-breast-milk-after-COVID-mRNA-vaccination.aspx. (accessed July 16, 2024).

  • Harvard

    Robertson, Sally. 2023. Vaccine mRNA not found in breast milk after COVID mRNA vaccination. News-Medical, viewed 16 July 2024, https://www.news-medical.net/news/20210309/Vaccine-mRNA-not-found-in-breast-milk-after-COVID-mRNA-vaccination.aspx.

Comments

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment
Post

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.

You might also like...
Real-world data confirms safety of RSV vaccination in late pregnancy