After being alerted to a potential safety issue about the bivalent shot in November, the two agencies investigated whether ischemic strokes were more likely to happen within 21 days post-vaccination versus between 22 and 42 days, the CDC said in a statement.
The CDC listed five analyses to confirm the lack of a risk:
- A large study of updated bivalent vaccines using the CMS database revealed no increased risk of ischemic stroke.
- A preliminary study using the Veterans Affairs database did not indicate an increased risk of ischemic stroke following an updated vaccine.
- The Vaccine Adverse Event Reporting System managed by CDC and FDA has not seen an increase in reporting of ischemic strokes following the updated vaccine.
- Pfizer-BioNTech’s global safety database has not indicated a signal for ischemic stroke with the updated vaccine.
- Other countries have not observed an increased risk for ischemic stroke with updated vaccines.
The CDC said it will continue tracking data on vaccine safety.
