Moderna’s bivalent shot has not been linked to this safety issue.

An extensive scientific examination found no evidence to support concerns that Covid booster shots produced by Pfizer-BioNTech may raise the risk of stroke in adults 65 and older, federal officials said on Friday.

The risk is “extremely unlikely” to actually exist, according to the officials, urging Americans aged 6 months and older to continue obtaining booster doses. Federal officials opted to make the concern and the findings of their inquiry public to quell concerns.

“We believe it is important to share this information with the public,” a joint statement from the Centers for Disease Control and Prevention and the Food and Drug Administration said.

Concerns about a potential connection to ischemic strokes, which can stop the flow of blood to the brain, initially surfaced in the latter part of last year. That signal was distinctive to the Pfizer-BioNTech bivalent vaccination and not linked to the original Covid vaccines or to Moderna’s bivalent boosters.

However, gathering information from other vaccine safety databases, as well as observations from the United States and other countries, the investigators found no proof of an elevated risk of strokes in any of these sources, the federal officials stated in their statement.

At a meeting of the FDA’s scientific advisors on upcoming Covid vaccinations, federal officials expect to address the findings on 26 January.

130 ischemic strokes among the approximately 550,000 seniors 65 and older who had received the Pfizer-BioNTech bivalent booster occurred 21 days following the shot, leading to concerns that the two incidents may have been connected. However, an alternative technique of data analysis failed to identify an elevated risk of ischemic stroke.

“There is no evidence to conclude that ischemic stroke is associated with the use of the companies’ Covid-19 vaccines,” Pfizer and BioNTech said in a statement. 

The prompted move came as the upgraded Covid-19 vaccine booster made by American pharmaceutical company Pfizer Inc. and German partner BioNTech was suspected of its association with a type of brain stroke in older adults, a safety monitoring system warned.

The Food and Drug Administration (FDA) and the US Centers for Disease Control and Prevention (CDC) were looking into a “preliminary signal” that suggested patients who received the updated Covid-19 vaccination booster from Pfizer and BioNTech may have a higher risk of stroke, according to preliminary data analysed by those United States health bodies.

Brain ischemia, another name for an ischemic stroke, is brought on by blockages in the arteries that provide blood to the brain.

A bivalent Covid-19 vaccine may also be referred to as ‘updated’ Covid-19 vaccine booster dose.

Calling the findings highly preliminary, the CDC said that “no other safety systems have shown a similar signal and multiple subsequent analyses have not validated this signal.”

The CDC’s Vaccine Adverse Event Reporting System, other nations’ databases, Pfizer-BioNTech databases, other sizeable studies, and the FDA’s databases, according to the FDA and CDC, did not identify this safety problem, emphasising that further research is needed.

“Although the totality of the data currently suggests that it is very unlikely that the signal in VSD (Vaccine Safety Datalink) represents a true clinical risk, we believe it is important to share this information with the public,” the health authorities said.

“Often these safety systems detect signals that could be due to factors other than the vaccine itself,” CDC said. The CDC and FDA continue to advise that everyone aged six months and older maintain current Covid-19 immunisation records.

House Energy and Commerce Chair Cathy McMorris Rodgers responded to the statement by announcing that the CDC and FDA will testify before her committee.

“These agencies must rapidly investigate, in an open and transparent manner, whether or not the vaccine may have contributed to the reported strokes,” McMorris Rodgers said in a statement.

Separately, since the introduction of the vaccines, there have been certain uncommon but serious side effects, which can happen with any pharmaceutical medication.

The second dosage of the mRNA vaccine has been linked to an increased risk of myocarditis and pericarditis — inflammation of the heart muscle and membrane, respectively — in males aged 12 to 39, with late adolescent and early adult males being most susceptible.

The FDA and CDC claim that the advantages of immunisation outweigh the hazards because the condition can also arise after infection with Covid and other illnesses, and tends to be more severe in those circumstances.