No Evidence Woman’s Breasts Grew to Triple G-Cup After Receiving COVID-19 Vaccine

A rumor that a teenager experienced significant breast enlargement after receiving a dose of the Pfizer COVID-19 vaccine circulated widely online in early January 2025. The claim that her breasts grew from a B-cup to a triple G-cup gained traction on numerous social media platforms and websites.

For example, an X post by the New York Post read (archived): “Teen’s breasts grew to triple G-cup size following COVID vaccination: ‘Concerns not adequately addressed.'” That post, which had amassed more than 600,000 views as of this writing, included a link that directed users to the newspaper’s article on the topic.

The claim spread on X, Instagram and news media websites such as the Daily Mail and AOL and on health news website Medical Daily.

One well-known, right-wing political commentator also posted the rumor on YouTube and suggested the vaccine caused the breast growth. He stated in his video (from 0:45 onward): “Maybe it’s a coincidence, but it really does seem like it correlates … it’s possible it’s unrelated, but I will stress it really does, according to the story, appear that it was the vaccine that caused the breast growth.” An X user also tried to link the vaccine to the woman’s breast enlargement.

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In short, a team of researchers confirmed that a teenager did experience “rapid” and “massive” breast growth after receiving a dose of the Pfizer COVID-19 vaccine. However, they also stated that, as of this writing, they had not established a causal link between the vaccine and her breast enlargement. Given that some social media posts tried to link the two, we have rated this claim as a mixture of true and false information.

Authentic Case Report, But Not Full Study

The news articles and social media posts were referring to an authentic case report published in the Plastic & Reconstructive Surgery–Global Open journal in December 2024. The report was titled: “The ‘Pfizer Boob Job’: A Case of Unexplained Gigantomastia.” As explained in the report, gigantomastia is a “rare condition characterized by rapid, diffuse, and excessive breast growth.”

However, a case report is not the same as a scientific study. A case report typically details observations or specific instances involving one individual, providing anecdotal evidence without broader statistical analysis. In contrast, scientific studies, particularly those that are peer-reviewed and include larger sample sizes, are designed to test hypotheses, establish causality and yield generalizable conclusions based on rigorous methodology. If enough case reports produce similar findings, they can lead to peer-reviewed studies being conducted.

This specific case report authentically detailed a 19-year-old Canadian woman’s “rapid” and “massive” breast enlargement from a B-cup to a triple G-cup, beginning one week after receiving the Pfizer COVID-19 vaccine. The report’s abstract read (emphasis ours):

True parenchymal breast changes following COVID-19 vaccination are exceedingly rare. Equally rare are incidences of pseudoangiomatous stromal hyperplasia (PASH)–associated gigantomastia. The patient in this case report presented with both occurrences and experienced massive breast enlargement 1 week postadministration of the Pfizer/BioNTech COVID-19 vaccine, which worsened after her second dose. [ …] The association between the COVID-19 vaccine, PASH, and breast hypertrophy warrants further investigation to comprehend the spectrum of reactions to the vaccine.

You can read the full report here:

Temporal Association, Not Causality

Although the case report was authentic, its “Conclusion” section stated that the cause of her breast growth “remains unclear,” and it recommended further research to explore any “potential link between the Pfizer vaccine, gigantomastia, and PASH” — PASH is “a benign (non-cancer) breast condition” that “is usually felt as a painless lump in the breast,” according to Breast Cancer Now, a research and support charity.

The report’s introduction said the case was the first of its kind “to demonstrate a temporal association between PASH-associated gigantomastia and a vaccine.” A temporal association or temporal relationship is a connection “between events or phenomena that occur over time” that is “crucial for understanding how things are linked based on when they happen.”

However, the “Discussion” section also stated that “a temporal relationship does not establish causality.”

The report acknowledged that some social media users “have claimed to experience breast growth,” which has been referred to as the “Pfizer boob job,” after receiving the pharmaceutical company’s COVID-19 vaccine. However, it stated that this is likely due to a separate, known side effect of the vaccine — axillary lymphadenopathy, which occurs when your underarm (axilla) lymph nodes grow larger in size — which is temporary in nature and “contribute[s] only to the perception of breast growth.” The introduction read:

Although axillary lymphadenopathy is a known side effect of COVID-19 mRNA vaccines, such changes are transient and contribute only to the perception of breast growth. To date, there has been only 1 published case outlining lasting parenchymal breast changes, presenting as a palpable mass, following administration of the Pfizer COVID-19 mRNA booster. No formal studies have established a link between breast parenchymal growth and the Pfizer COVID-19 vaccine. Although these social media claims have been disputed by the New Zealand Ministry of Health, more research is needed to further investigate these findings.

Dr. Kathleen Armstrong, one of the report’s authors, clarified via email that the study found “no causal link” between the Pfizer COVID-19 vaccine and the development of gigantomastia in the reported case, adding that the findings reflect “only a chronological correlation.”

She further explained that the report did not propose or investigate any “speculated mechanism of action” — a hypothetical explanation or theory — to suggest how the vaccine might be connected to PASH-associated gigantomastia. In other words, there has been no exploration or suggestion of how the vaccine might be connected to the condition and the idea remains entirely speculative.

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