Safety Signal in Seniors Prompts Investigation of Bivalent COVID-19 Vaccine

Patient getting vaccinated.
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The preliminary safety signal was identified by the CDC’s Vaccine Safety Datalink.

The Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) are investigating a potential safety concern with the Pfizer-BioNTech bivalent COVID-19 vaccine in individuals 65 years of age and older.

The preliminary safety signal was identified by the CDC’s Vaccine Safety Datalink (VSD), a near real-time surveillance system. Specifically, the signal raised a question of whether individuals 65 years of age and older who received the Pfizer-BioNTech COVID-19 Vaccine, Bivalent were more likely to have an ischemic stroke in the 21 days after vaccination compared with days 22 to 44 post vaccination. The safety signal was not identified with the Moderna COVID-19 Vaccine, Bivalent.

The signal prompted further investigation into other vaccine safety monitoring systems. Findings from the Centers for Medicare and Medicaid Services database, as well as the Veteran Affairs database, have not shown a similar increase in the risk of ischemic stroke with the bivalent vaccines. There has also been no increase in reporting of ischemic stroke following administration of the bivalent booster, according to the FDA’s Vaccine Adverse Event Reporting System (VAERS). Similarly, the Pfizer-BioNTech global safety database has not indicated a signal for ischemic stroke.

In a press statement, the FDA noted that based on the totality of evidence it appears to be “very unlikely that the signal in the VSD represents a true clinical risk.” The FDA and CDC said they would continue to evaluate data from multiple safety monitoring systems. The FDA’s Vaccines and Related Biological Products Advisory Committee will also be reviewing the additional analyses at an upcoming meeting on January 26, 2023.

At this time, there have been no changes to recommended COVID-19 vaccination practice. Individuals are encouraged to stay-up-to date with COVID-19 vaccination, including receiving the bivalent vaccine.


CDC and FDA identify preliminary COVID-19 vaccine safety signal for persons aged 65 years and older. News Release. January 13, 2023. Accessed January 17, 2023.