Close-up image of vaccination being given in upper arm of older individual

Seniors are “very unlikely” to experience an ischemic stroke soon after receiving Pfizer-BioNTech’s bivalent COVID vaccine booster, the Centers for Disease Control and Prevention reported Friday.

The agency’s Vaccine Safety Datalink (VSD) has flagged a potential risk of stroke among adults aged 65 years and older within 21 days following vaccination with the Pfizer shot, when compared to 22 to 42 days. The VSD is a near real-time surveillance system of adverse vaccine events, and the CDC said that it is sharing the information with the public in the interest of transparency. But the combined evidence from a number of data tracking sources does not support heightened concern, it added.

No change in guidance

No other safety databases flagged the stoke risk for the Pfizer vaccine, which was authorized in August, and there was no such signal for Moderna’s equivalent vaccine, the CDC noted. Although the agency will continue to investigate, there will be no changes to the recommendation that all eligible people receive the shot, especially older adults and others vulnerable to severe COVID-19, it said.

In the meantime, there has been no increased risk of ischemic stroke found in a large study of the updated, bivalent vaccines that used data from the Centers for Medicare & Medicaid Services. There was also no risk found in a preliminary study from the Veterans Affairs database, or in data from the manufacturers, or from another event reporting system managed by the CDC and Food and Drug Administration. There also has been no indication of increased ischemic stroke risk from other countries, the CDC reported.

The CDC and FDA “will continue to evaluate additional data from these and other vaccine safety systems,” the agency stated. The FDA’s vaccine advisers plan to discuss the current data at an upcoming Jan. 26 meeting.

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