The Centers for Disease Control and Prevention on Friday said it was “unlikely” that Pfizer’s omicron booster posed a stroke risk to the elderly after launching an investigation into an initial safety issue detected by one of its monitoring systems.
The CDC, in a statement posted to its website on Friday, said a surveillance system called Vaccine Safety Datalink detected a possible risk of stroke in people aged 65 and over who received the Pfizer booster shot targeting the omicron variant of Covid. A CDC spokesperson said the problem was first detected in late November.
In mid-December, the CDC concluded the concern was persistent and launched an investigation into whether older people were more likely to have a stroke in the first 21 days after receiving the Pfizer booster, a spokeswoman said. A similar initial signal was not detected for the Moderna booster.
The VSD monitoring system found that 130 people age 65 and older had a stroke within 21 days of receiving Pfizer’s omicron booster among 550,000 older adults who received the shot, a CDC spokeswoman said. No deaths were reported. The Washington Post previously reported the news.
No other surveillance system has detected similar safety concerns for Pfizer’s booster so far, according to the CDC. Investigators did not find an increased risk of stroke after the Pfizer booster after reviewing data from the Centers for Medicare and Medicaid Services, the Department of Veterans Affairs, the Vaccine Adverse Reporting System and Pfizer’s global safety database.
“Although the total data now shows that it is unlikely that the signal in the VSD indicates a true clinical risk, we believe that it is important to share this information with the public, as it has been in the past, when one of our safety monitoring systems detected a signal,” he said. CDC in a post on its website.
Monitoring systems often detect safety signals due to factors other than vaccines, according to the CDC’s Friday statement. A spokeswoman for the agency said investigators have a clearer picture and more data in the coming weeks.
The investigation will be discussed at a Food and Drug Administration panel of independent vaccine experts meeting on January 26.
In a statement on Friday, Pfizer said there was no evidence to conclude that ischemic strokes were linked to the company’s Covid vaccine. Neither Pfizer nor its German partner BioNTech, nor the CDC or FDA, have seen the association in many other monitoring systems in the US and globally, said company spokesman Kit Longley.
“Compared to the incidence rate of ischemic stroke published in this older population, the company has so far experienced a lower number of ischemic strokes after vaccination with the bivalent vaccine adapted omicron BA.4 / BA.5,” said Longley.
The CDC has not changed its recommendations for Pfizer’s omicron shot. Everyone age 5 and older is eligible for a booster after completing the primary vaccine series. The youngest children aged 6 months to 4 years receive omicron injection as the third dose of the primary series.