The US Centers for Disease Control and Prevention said on Friday that there is a possible safety concern with the bivalent Covid-19 vaccine being developed by Pfizer and BioNTech, but that it is unlikely to represent a real risk. The agency said it continues to advise people to be up-to-date on their Covid-19 vaccinations.
The CDC said one of its vaccine safety monitoring systems — a “near real-time surveillance system” called the Vaccine Safety Data Link — recently detected a possible increase in certain types of stroke in people 65 and older who received one of Pfizer’s updated booster shots. .
A rapid response analysis of this signal showed that older adults receiving bivalent boosters may be more likely to have an ischemic stroke in the first three weeks after shots compared to four to six weeks.
Ischemic strokes, the most common form, are blockages of blood flow to the brain. They are usually caused by clotting.
Vaccine Safety Datalink, or VSD, is a large nationwide network of health systems that provide information on the safety and effectiveness of vaccines through patients’ electronic health records. The CDC said it identified possible confounding factors in the data from the VSD that could bias the data and need further investigation.
According to a CDC official who spoke to CNN on condition of anonymity, 130 of the nearly 550,000 seniors who received the Pfizer bivalent boosters and were followed by VSD had a stroke within three weeks of the shots because they were not authorized to share the data. . None of the 130 people died.
Dr. William Schaffner said the number of detected hits was relatively small.
“These strokes are not a confirmed adverse event at this time,” he said. “It’s like a radar system. You get a hit on the radar and you need to investigate further to see if this aircraft is friend or foe.”
The same safety signal was not detected with the bivalent Moderna amplifier, the CDC notice said.
The agency noted that it searched and failed to find the same increase in strokes in other large collections of medical records, including Medicare, the U.S. Department of Veterans Affairs, and other large collections known as the Vaccine Adverse Event Reporting System. VAERS.
Neither Pfizer nor other countries using the vaccine have seen any increase in this type of stroke, the agency said, and the signal has not been detected in other databases.
The CDC says it is not currently recommending any changes in vaccination practices and that the risks of Covid-19 for older adults continue to outweigh any safety concerns about the vaccine.
“Although the body of data now suggests that the signal in VSD is very unlikely to represent a true clinical risk, we believe it is important to share this information with the public, as we have in the past. monitoring systems detect a signal,” the notice reads.
“CDC and FDA will continue to evaluate additional data from this and other vaccine safety systems. These data and additional analysis will be discussed at the January 26 meeting of the FDA’s Vaccines and Related Biological Products Advisory Committee.
Pfizer said in a statement Friday, “Neither Pfizer and BioNTech, nor the CDC, nor the US Food and Drug Administration (FDA) have observed similar findings in numerous other monitoring systems in the United States and globally, and there is no evidence to conclude that ischemic stroke No. related to companies’ use of COVID-19 vaccines.
“Compared to the published incidence of ischemic stroke in this elderly population, companies have observed fewer reported ischemic strokes after vaccination with the Omicron BA.4/BA.5-adapted bivalent vaccine to date.”
Bivalent enhancers from Pfizer/BioNTech and Moderna protect against the original strain of the coronavirus, as well as the Omicron BA.4 and BA.5 subvariants. According to the CDC, only about 50 million Americans ages 5 and older have gotten them since they were authorized last fall.
Schaffner said he attended a briefing with members of the Covid-19 Vaccine Task Force on Thursday. He could not share specific details about the briefing, but said a security alert was discussed.
His biggest suggestion was the operation of the security control system.
It’s probably a false alarm, he said, but it’s being investigated, which is important.
“You want a control system that periodically sends false alarms. “If you don’t get any signal, you worry that things are missing.”
Schaffner said she would definitely tell people to get the Covid-19 booster if they haven’t already, even those 65 and older.
“Certainly, the risk of a number of adverse events, including hospitalization, is much, much greater with the Covid-19 vaccine,” he said.
He also said the signal — if real — could be more a factor in numbers than an indication that one manufacturer’s vaccine is riskier than another.
About two-thirds of the people in the U.S. who got the updated booster — 32 million — got Pfizer, compared with about 18 million Moderna shots.