CDC Exploring Possible But Unlikely Link Between Covid-19 Bivalent Booster And Strokes

Published 1 year ago
Injection of the third dose of the covid 19 vaccine at a Covid-19 vaccination center in Dinan, Brittany


The Centers for Disease Control and Prevention and the Food and Drug Administration said Friday a possible link has been identified between Pfizer-BioNTech’s bivalent Covid-19 vaccine and ischemic strokes in people over the age of 65 who received the shot, however the agencies are not recommending any changes to vaccine distribution.


The CDC’s Vaccine Safety Datalink surveillance system detected data that “raised a question” as to whether people over the age of 65 who received that specific Pfizer vaccine were more likely to have an ischemic stroke in the first 21 days following their inoculation, compared to between 22 and 44 days after.

The statement said no other safety signals have detected this potential issue, and neither have studies of data from the Centers for Medicare and Medicaid Services, Veterans Affairs, the Vaccine Adverse Event Reporting System and Pfizer-BioNTech.


No such signal has been detected with Moderna’s bivalent vaccine.

The data suggests it’s “very unlikely” this signal represents “a true clinical risk,” the CDC said, and the agency and the FDA will continue to evaluate data regarding this issue.


15.9%. That’s how many Americans who are aged five and older have received an updated booster dose, according to the CDC.


Known as “updated boosters,” the bivalent shots became available to those 12-years-old and older in September, those ages 5 to 11 in October, and to some children between the ages six months and four years old in December. These shots contain mRNA from both the original strain of Covid-19, and those related to the BA.4 and BA.5 subvariants of the omicron strain, which was one of the most popular strains of the virus last year. A CDC study released in December found that the bivalent doses were 56% more effective in preventing Covid compared to no vaccine. And those who received the dose were 50% less likely to contract Covid-19 than those who received the initial dosage at least 11 months earlier. The updated booster also greatly decreased the risk of hospitalization, compared to unvaccinated adults.