Possible Bivalent Vaccine Link to Strokes in People Over 65

Ralph Ellis

January 17, 2023

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

A vaccine database found a possible link between the Pfizer/BioNTech bivalent COVID-19 vaccine and ischemic strokes in people over 65 who got the shot, the CDC and the FDA said in a joint news release.

The release did not recommend people change their vaccine practices, saying the database finding probably did not represent a "true clinical risk." The CDC said everybody, including people over 65, should stay up to date on their COVID vaccines, including the bivalent booster.

The news release said the Vaccine Safety Datalink (VSD), "a near real-time surveillance system," raised a safety concern about the Pfizer/BioNTech booster.

"Rapid-response investigation of the signal in the VSD raised a question of whether people 65 and older who have received the Pfizer-BioNTech COVID-19 Vaccine, Bivalent were more likely to have an ischemic stroke in the 21 days following vaccination compared with days 22-44 following vaccination," the news release said.

Ischemic strokes are blockages of blood to the brain, often caused by blood clots.

"Although the totality of the data currently suggests that it is very unlikely that the signal in VSD (Vaccine Safety Datalink) represents a true clinical risk, we believe it is important to share this information with the public, as we have in the past, when one of our safety monitoring systems detects a signal." the release said.

No higher likelihood of strokes linked to the Pfizer bivalent vaccine had been found by Pfizer/BioNTech, the Veterans Administration, the Vaccine Adverse Event Reporting System (VAERS) maintained by the CDC and the FDA, or other agencies that monitor reactions of vaccines, the news release said. No safety issues about strokes have been identified with the Modera bivalent vaccine. 

CNN, citing a CDC official, reported that about 550,000 seniors who got Pfizer bivalent boosters were tracked by the VSD, and 130 of them had strokes within three weeks of getting the shot. None of those 130 people died, CNN said. The official spoke on the condition of anonymity because they weren't authorized to share the data. 

The issue will be discussed at the January meeting of the FDA's Vaccines and Related Biological Products Advisory Committee.

In a joint statement, Pfizer and BioNTech said: "Neither Pfizer and BioNTech nor the CDC or FDA have observed similar findings across numerous other monitoring systems in the U.S. and globally and there is no evidence to conclude that ischemic stroke is associated with the use of the companies' COVID-19 vaccines."

Bivalent boosters contain two strains of vaccine – one to protect against the original COVID-19 virus and another targeting Omicron subvariants.

Sources

FDA. "CDC and FDA Identify Preliminary COVID-19 Vaccine Safety Signal for Persons Aged 65 Years and Older"

CNN. "CDC identifies possible safety issue with Pfizer's updated Covid-19 vaccine but says people should still get boosted"

CDC: Vaccine Safety Datalink

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