COVID‐19 mRNA Vaccine associated Cerebral Venous Thrombosis: Rare Adverse Event or Coincidence?

Rare cases of cerebral venous thrombosis after COVID-19 mRNA vaccines have been reported in real-world post-vaccination data. As phase 3 clinical mRNA vaccine trials do not aim to and are not sufficiently powered to detect rare adverse events, the risks, and benefits of new vaccines are usually not fully known during regulatory approval, particularly following emergency use authorization. A temporal relation to vaccine administration does not confirm the diagnosis of “vaccineinduced thrombosis.” In addition, available literature on postvaccination thrombosis lacks sufficient power to detect significant associations with rare events like CVT. Hence, we discuss our observations of cerebral venous thrombosis occurring after COVID-19 mRNA vaccination in Singapore.