Brain blood clots a much higher risk after COVID-19 than after an mRNA vaccine

Embargoed until: Publicly released: 2022-03-18 02:00

International

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Cerebral venous thrombosis (CVT), or a brain blood clot, is far more likely to occur after a COVID-19 infection than after vaccination with Pfizer or Moderna, according to a study out of Singapore. CVT is an extremely rare but possible side effect of the mRNA vaccines, so researchers used Singapore hospital data to estimate the rate of the condition after vaccination and compare it to the rate after COVID-19. The researchers say six CVT cases were identified among just over 60,000 COVID-19 patients, and nine CVT cases were identified among 3 million people vaccinated with Pfizer or Moderna. The researchers estimate 83.3 people per 100,000 will develop CVT after COVID-19, compared to 2.59 people per 100,000 who get vaccinated. They say the low rate and disproportionately high age of vaccine recipients could have influenced the study, as could a potential underreporting of asymptomatic COVID-19 cases in the country.

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Journal/
conference: JAMA Network Open

Research:Paper

Organisation/s: National Neuroscience Institute, Singapore

Funder: Dr Tu reported being a member of the neurology expert panel for the Singapore Health Sciences Authority advising on thrombotic events related to COVID-19 vaccines. Dr Yeo reported receiving Cereflo shares and grants from NMRC outside the submitted work. Dr K. Tan reported receiving personal fees from Novartis, Merck, Sanofi, Eisai, Viela Bio, and Roche outside the submitted work. No other disclosures were reported.

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