The Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) in the United States said on Friday that their surveillance system flagged a link between the updated Pfizer-BioNTech bivalent Covid-19 vaccine and a higher risk of stroke in adults.
The bivalent vaccine is an updated vaccine that targets two versions of the coronavirus: the original strain and the Omicron subvariants BA.4 and BA.5.
According to CNN, the CDC said one of its vaccine safety monitoring systems – a “near real-time surveillance system” called the Vaccine Safety Datalink – detected a possible increase in a certain kind of stroke in people 65 and older who recently got one of Pfizer’s updated booster shots.
“A rapid response analysis of that signal revealed that seniors who got an bivalent booster might be more likely to have ischemic strokes within the first three weeks after their shots, compared with weeks four through six,” CNN reported.
An ischemic stroke, also known as brain ischemia, is caused by blockages in arteries that carry blood to the brain.
The FDA and CDC, however, noted that other large studies, the CDC’s Vaccine Adverse Event Reporting System, other countries’ databases and Pfizer-BioNTech’s databases had not flagged this safety issue, adding that it requires more investigation.
In response, Pfizer and BioNTech said in a statement that neither Pfizer and BioNTech nor the CDC or FDA have observed similar findings across numerous other monitoring systems in the U.S. and globally.
“There is no evidence to conclude that ischemic stroke is associated with the use of the companies’ COVID-19 vaccines,” the companies added.
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