The Centers for Disease Control and Prevention (CDC) announced Friday that it has launched an “additional investigation” into Pfizer’s updated COVID booster after a government safety monitoring system detected a potential stroke risk for those 65 and older who received the pharmaceutical giant’s bivalent shot.
Bivalent COVID vaccines were authorized by the FDA last August to provide greater protection against the virus as it progressed into different strains, such as the Omicron variant. The updated boosters include a component of the original COVID strain along with a component from Omicron, according to the FDA.
“CDC’s Vaccine Safety Datalink (VSD), a near real-time surveillance system, met the statistical criteria to prompt additional investigation into whether there was a safety concern for ischemic stroke in people ages 65 and older who received the Pfizer-BioNTech COVID-19 Vaccine, Bivalent,” the CDC said in a statement.
The concerning VSD signal has caused the agency to question whether those 65 and older who received Pfizer’s bivalent COVID vaccine were at an increased risk of having an ischemic stroke up to three weeks after their vaccination compared to 22-44 days after the shot. The CDC said Moderna’s bivalent COVID vaccine was not identified for the same risk by its monitoring system.
The CDC added that there “may be other confounding factors contributing” to the VSD’s signaling of the Pfizer vaccine and emphasized that other studies conducted on Pfizer and Moderna bivalent vaccines did not validate the signal. Furthermore, the agency said that there has not been any increase in reports in the U.S. or other countries of ischemic strokes following the updated vaccine.
“Although the totality of the data currently suggests that it is very unlikely that the signal in VSD represents a true clinical risk, we believe it is important to share this information with the public,” the CDC said.
The new investigation from the government agency has not resulted in any change to its vaccination recommendations, and the CDC continues to urge “everyone ages 6 months of age and older stay up-to-date with COVID-19 vaccination,” including those “eligible to receive an updated (bivalent) vaccine.”