No blood clot cases linked with Moderna and Pfizer coronavirus vaccines, CDC expert says

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(CNN) — No blood clots have been associated with coronavirus vaccines made by Moderna or Pfizer, a US Centers for Disease Control and Prevention expert said Friday.

The CDC’s Advisory Committee on Immunization Practices is meeting to discuss whether to change guidance for J&J’s Janssen vaccine. The CDC and the US Food and Drug Administration recommended pausing its use after six reported cases of women who developed a rare blood clotting syndrome called thrombosis with thrombocytopenia syndrome, or TTS, after receiving Johnson & Johnson’s Janssen vaccine in the United States. But no cases have been firmly linked with other vaccines used in the US.

“Currently, there is a lack of evidence of an association between mRNA COVID-19 vaccines and (Cerebral venous sinus thrombosis) with thrombocytopenia,” the CDC’s Dr. Tom Shimabukuro told members of the CDC’s vaccine advisory group. J&J’s vaccine is made using a common cold virus called an adenovirus, while Moderna’s and Pfizer’s vaccines are made using raw genetic material called messenger RNA.

Shimabukuro told ACIP that 2.7 million doses of Pfizer/BioNTech coronavirus vaccine and 2.5 million doses of Moderna’s vaccine had been included in CDC’s Vaccine Safety Database as of April 17. He said 10 cases of a rare type of brain blood clot called CVST were reported afterward but five were ruled out because of the medical histories of the patients, and five more were ruled out because patients did not develop a low level of platelets. It’s the combination of blood clots and low platelet counts that is linked with the vaccines.

ACIP is expected to vote on any changes to its guidance for J&J’s vaccine later Friday. If ACIP recommends changes to the vaccine label — such as a warning, or changes to who it recommends should get the vaccine — CDC Director Dr. Rochelle Walensky will sign off and then the FDA will have to make any label changes.

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