Pfizer Inc.’s bivalent shot for Covid-19 has shown a potential link to stroke in people 65 and older, according to US health officials citing preliminary data from one of several vaccine safety databases.
The potential risk with Pfizer’s vaccine was not seen in other safety databases, nor was it seen with Moderna Inc.’s Covid vaccine, the officials said in a statement on the Food and Drug Administration’s website. The early finding still needs more investigation, and recommendations for the vaccine have not been changed, the statement said.
“When we find a signal we look for it in other parts of the system, which is what we’ve done (and will continue to do),” Kristen Nordlund, a spokesperson for the Centers for Disease Control and Prevention, said in an email.
The agencies said the possible link to stroke was seen in the CDC’s Vaccine Safety Datalink. Investigation of the signal raised a question of whether people 65 and older who received the Pfizer-BioNTech bivalent shot were more likely to have an ischemic stroke, a loss of blood flow in the brain, in the 21 days following vaccination compared with days 22-44 following vaccination, the agencies said in the statement.
“The totality of the data currently suggests that it is very unlikely that the signal in VSD represents a true clinical risk,” the statement said.
Pfizer’s bivalent booster is armed specifically to protect against two omicron variants, called BA4 and BA5. Messenger RNA Covid shots have been linked to pericarditis and myocarditis, inflammation of the heart and its surrounding tissue that’s usually mild.
Pfizer and its partner BioNTech Se “have been made aware of limited reports of ischemic stroke” in the CDC Vaccine Safety DataLink database in people 65 and older following vaccination after the companies’ bivalent shot, a spokesperson said. There is no data to conclude that Pfizer’s vaccine is causally associated with stroke, the spokesperson said.