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What you need to know

  • The CDC and FDA confirmed that older adults do not need to worry about an increased risk of stroke from Pfizer’s bivalent booster.
  • The agencies will continue to evaluate additional data from vaccine safety systems.
  • Data shows that bivalent boosters reduce the risk of COVID-19 hospitalization and death, especially for older adults.

Over the last week, concerns have been circulating about a potential link between Pfizer’s bivalent booster and an increased risk of stroke in older adults. Below, we address these concerns and clarify that the CDC and FDA found the boosters to be safe. In fact, bivalent, or updated, boosters are an important tool for protecting high-risk individuals as the now dominant XBB.1.5 Omicron subvariant continues its spread.

Is Pfizer’s bivalent booster linked to an increased risk of stroke in older adults?

No, the CDC and FDA describe such a link as “very unlikely.” The agencies confirmed on January 13 that older adults do not need to be worried about an increased risk of stroke from bivalent boosters. 

In November 2022, the Vaccine Safety Datalink (VSD), one of the CDC’s vaccine safety monitoring systems, detected a signal that Pfizer’s bivalent booster may be linked to an increased risk of stroke in people ages 65 and older. This signal prompted the CDC and FDA to investigate further. The agencies analyzed several large studies and vaccine safety databases—including those from VAERS, other countries’ regulators, and Pfizer-BioNTech. None of them showed similar findings. The results from this comprehensive data review led the CDC and FDA to conclude that an increased risk of stroke from Pfizer’s bivalent booster is “very unlikely.”

Should you be concerned about the original safety signal that VSD detected?

Being worried when you hear about a safety signal is understandable. But safety signals are not the same as a true vaccine safety risk. We have several vaccine safety monitoring systems (including VSD and VAERS) that are designed to be extremely sensitive. They can pick up on “safety signals,” or increased appearances of certain health issues, that may not be caused by the vaccine itself. Scientists take this information and investigate whether the signal actually indicates a true risk.

The recent case around Pfizer’s bivalent booster and a potential increased risk of stroke is evidence that our vaccine safety systems work. The CDC and FDA will continue to evaluate additional data from vaccine safety systems and will discuss their findings at the January 26 FDA advisory committee meeting.

Should older adults still get a bivalent booster?

Yes. The CDC, FDA, and other health care experts all agree that bivalent boosters are crucial for older adults and other high-risk individuals. 

With Omicron subvariant XBB.1.5 now the dominant strain in the U.S., it’s especially important for vulnerable people to stay up to date on their COVID-19 vaccinations. Many COVID-19 treatments don’t work against XBB.1.5, the most transmissible strain yet, so avoiding infection and hospitalization is key. Data has shown that bivalent boosters reduce the risk of COVID-19 hospitalization and death compared to people who are unvaccinated as well as people who are vaccinated but have not received a bivalent booster.

Both Pfizer’s and Moderna’s bivalent boosters are currently authorized for everyone ages 5 and older at least two months after their last shot. Some kids under age 5 are also eligible to receive a bivalent vaccine. You can find a bivalent booster near you at Vaccines.gov