The CDC and FDA announced on Friday that their surveillance system flagged a possible link between the new Pfizer-BioNTech bivalent Covid-19 vaccine and strokes in people aged 65 and over, but said they were continuing to recommend the shots.
The surveillance “raised a question of whether” stroke risk was elevated in the 21-day period post-vaccination versus 22 to 44 days post-vaccination, according to a statement on the CDC website.
The agencies said other data from the Centers for Medicare and Medicaid Services, Department of Veterans Affairs and other sources haven’t shown an elevated risk of stroke.
“Although the totality of the data currently suggests that it is very unlikely that the signal … 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,” the statement said.
The real-time surveillance system, CDC’s Vaccine Safety Datalink, met criteria warranting further investigation into whether the bivalent Pfizer vaccine led to a higher risk of ischemic stroke, which occurs when arteries pumping blood to the brain are blocked by a blood clot.
Pfizer and BioNTech said in a statement that there is “there is no evidence to conclude that ischemic stroke is associated with the use of the companies’ COVID-19 vaccines.”