Pfizer's bivalent Covid vaccine may be linked to stroke in older adults, US says

US drugmaker Pfizer Inc and German partner BioNTech's updated Covid-19 shot could be linked to a type of brain stroke in older adults, according to preliminary data analysed by US health authorities.

Citing one of many vaccine safety databases of the US Centres for Disease Control and Prevention (CDC), health officials said on Friday that people 65 and older were more likely to have an ischemic stroke 21 days after receiving the Pfizer/BioNTech bivalent shot, compared with days 22-44.

An ischemic stroke, also known as brain ischemia, is caused by blockages in arteries that carry blood to the brain.

The safety concern requires more investigation and "it is very unlikely that it represents a true clinical risk", the authorities said.

Pfizer and BioNTech said in a statement that they have been made aware of limited reports of ischemic strokes in people 65 and older following vaccination with their updated shot.

"Neither Pfizer and BioNTech nor the CDC or the U.S. Food and Drug Administration (FDA) have observed similar findings across numerous other monitoring systems in the U.S. and globally and there is no evidence to conclude that ischemic stroke is associated with the use of the companies' Covid-19 vaccines," Pfizer added.

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