Update on Pfizer COVID-19 bivalent booster

The following information was shared by the Washington State Department of Health:

On January 13, the CDC announced that they will be investigating a preliminary safety signal for the Pfizer Bivalent Booster.  The safety signal was detected by the CDC’s Vaccine Safety Datalink.  Other safety systems, databases, and countries are not seeing the same link, nor has it been seen in other brands of COVID Vaccine.

The signal is unlikely to represent a true clinical risk.  Please continue vaccinating patients with the bivalent COVID-19 vaccine when they are due. 

You can read more about the VSD Pfizer Bivalent safety signal here

Here is more detailed information:

  • CDC’s Vaccine Safety Datalink (VSD), one of several vaccine safety monitoring systems in place in the United States, has picked up a signal indicating a potential risk of ischemic stroke in adults over 65 who received the Pfizer-BioNTech COVID-19 bivalent booster. 
  • There is no signal for the Moderna COVID-19 bivalent booster. 
  • U.S. government agencies use multiple, complementary safety monitoring systems to help detect possible vaccine statistical signals as early as possible and to know when or if to investigate a possible issueVSD, the system that picked up this signal, is one of these. 
  • As a response to this signal in the VSD, the CDC worked with the U.S. Food and Drug Administration to further investigate this potential side effect in other safety monitoring systems (such as VAERS) and clinical databases (including those for Medicare, the VA, Israel, and some European countries). No clinical risk of ischemic stroke has been identified in other sources. 
  • Other countries have not observed an increased risk for ischemic stroke with bivalent vaccines. 
  • Pfizer-BioNTech’s global safety database also does not indicate a signal for ischemic stroke with this vaccine.

What does this mean for clinicians?

  • Overall, the totality of the data suggests it is very unlikely that the signal in VSD represents a true clinical risk. In the spirit of transparency, CDC wanted to share this early information with the public. 
  • No change in vaccination practice is recommended. 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. 
  • Public health supports the continued assessment of vaccine safety. The finding from the Vaccine Safety Datalink shows that the system is working, and we are being vigilant in detecting any adverse health outcomes associated with the COVID-19 vaccine. 

What’s next?

CDC and FDA will continue to evaluate additional data from the VSD and other vaccine safety systems. These data and additional analyses will be discussed at the upcoming January 26 meeting of the FDA’s Vaccines and Related Biological Products Advisory Committee.