A CDC vaccine database revealed that people aged 65 and older were more likely to have an ischemic stroke 21 days after receiving the Pfizer/BioNTech bivalent shot, compared with days 22-44.
The FDA and CDC said that other large studies, the CDC's Vaccine Adverse Event Reporting System, other countries' databases, and Pfizer-BioNTech's databases had not flagged this safety issue and that it requires more investigation.
Pfizer and BioNTech also said they had been made aware of limited reports of ischemic strokes in people 65 and older following vaccination with their updated shot. However, there is no evidence to conclude that ischemic stroke is associated with using the companies' COVID-19 vaccines.
CDC and FDA Continue to Recommend COVID-19 Vaccination For All Aged Six Months and Older
Despite the possible safety issue, Moderna's bivalent shot has not identified the safety concern. The CDC and FDA recommend that everyone aged six months and older stay up-to-date with their COVID-19 vaccination.