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Critique of testing for new COVID-19 vaccine misunderstands old study | Fact check

Joedy McCreary   Paste BN

The claim: The new COVID-19 vaccine was tested on only four rats

A Sept. 12 Instagram post (direct link, archive link) shows a screenshot of a post on X, formerly Twitter, about a newly approved COVID-19 vaccine.

“The new FDA-approved COVID shots were tested on four rats,” reads part of the post. "Yes, four rats. Four. Rats."

It received more than 400 likes in one day. The original X post was shared more than 9,000 times in one day.

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Our rating: False

The post misinterprets a study that involved 44 rats, not four. And it was published in 2021, long before the latest version of the vaccine was developed.

Study looked at 44 rats, not four

The social media posts appear to reference the Sept. 12 approval of an updated version of the COVID-19 vaccine by the Food and Drug Administration and the Centers for Disease Control and Prevention. The new version targets recent variants of the disease.

Fact check: COVID-19 vaccine makers did not halt animal tests, and there were no widespread animal deaths

The screenshot in the Instagram post includes the first of a three-post thread on X.

The second post in that series contains an image of a paragraph from a document Pfizer published in October 2022. The information sheet was distributed to health care providers administering the COVID-19 vaccine and discusses a study evaluating its safety in pregnant rats.

While a description of that study is included in a fact sheet for the new booster, the phrasing differs from the version in the X post. Nowhere in either document does it specify how many rats were involved in the study. Rather, both documents state that the female rats were injected a total of four times – 21 and 14 days before mating, and on the ninth and 20th days of gestation.

That study itself was published in May 2021, and predates the new booster by more than a year. It was conducted by researchers from Pfizer, BioNTech and Charles River Laboratories in France.

A total of 44 female rats received the Pfizer vaccine, according to the study. Half delivered their pups by Caesarean section, and the other half delivered them naturally. The research found no adverse vaccine-related effects on female fertility or fetal or postnatal development.

Paste BN reached out to the study’s lead author, Pfizer research fellow Christopher J. Bowman, but did not immediately receive a response.

Data from numerous studies shows that receiving a COVID-19 vaccine during pregnancy "was not associated with an increased risk for pregnancy complications, including preterm birth, stillbirth, bacterial infection of the placenta and excessive maternal blood loss after birth," according to the CDC.

The CDC states the vaccines are safe for pregnant people and recommends that everyone aged 6 months and older, including people who are pregnant, receive the COVID-19 vaccine and boosters.

Paste BN reached out to the social media users who shared the post but did not immediately receive responses.

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