CDC, FDA Announce Safety Signal Related to the Pfizer-BioNTech Bivalent COVID-19 Vaccine

The FDA and Centers for Disease Control and Prevention (CDC) issued a joint statement on Friday that was written on the latter’s website and informed the public the two agencies were evaluating the data into whether one of the bivalent vaccines increased the risk of ischemic stroke in the senior population.

“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/FDA statement read. “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 22-42 following vaccination.”

On the CDC website, they also said government agencies use various monitoring systems to detect possible safety signals for vaccines. They will investigate further when appropriate. “Often these safety systems detect signals that could be due to factors other than the vaccine itself,” the website read.

FDA and CDC also said this preliminary signal was not identified in the Moderna bivalent vaccine. To date, only the Moderna and Pfizer-BioNTech vaccines are using mRNA technology. 

The agencies pointed to other studies and surveillance systems reporting the following:

• A large study of updated (bivalent) vaccines (from Pfizer-BioNTech and Moderna) using the Centers for Medicare and Medicaid Services 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 (bivalent) vaccine
• The Vaccine Adverse Event Reporting System (VAERS) managed by CDC and FDA has not seen an increase in reporting of ischemic strokes following the updated (bivalent) vaccine
• Pfizer-BioNTech’s global safety database has not indicated a signal for ischemic stroke with the updated (bivalent) vaccine
• Other countries have not observed an increased risk for ischemic stroke with updated (bivalent) vaccines

As such, the CDC is recommending no change in the vaccination practice. “CDC continues to recommend that everyone ages 6 months of age and older stay up-to-date with COVID-19 vaccination; this includes individuals who are currently eligible to receive an updated (bivalent) vaccine,” the joint statement read.

According to CDC, VSD is an ongoing, collaboration project between the CDC’s Immunization Safety Office, integrated health care organizations, and networks across the US. The VSD has been in existence for over 30 years and monitors the safety of vaccines and conducts studies about rare and serious adverse events following immunization. There are 13 VSD sites that provide clinical, methodological, and data expertise.

FDA and CDC wanted to make it clear they were being transparent and inform the public they were reviewing the data.

“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, as we have in the past, when one of our safety monitoring systems detects a signal. CDC and FDA will continue to evaluate additional data from these and other vaccine safety systems.”

In addition, at the next FDA Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting on January 26, data and additional analyses will be presented on this safety signal to this FDA advisory committee. They had already planned to meet to discuss if the currently available COVID-19 vaccines should be modified and how and whether the composition and schedule for booster doses should be adjusted moving forward.