CDC identifies a possible safety issue with Pfizer’s updated Covid-19 vaccine, but says people should be refreshed anyway

CDC identifies a possible safety issue with Pfizer's updated Covid-19 vaccine, but says people should be refreshed anyway
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The U.S. Centers for Disease Control and Prevention said Friday there is possible security issue with the Pfizer and BioNTech bivalent Covid-19 vaccine, but that it is unlikely to pose a real risk. The agency said it continues to recommend that people stay informed about Covid-19 vaccines.

The CDC said one of its vaccine safety monitoring systems — a “near-real-time monitoring system” called Vaccine Safety Datalink — detected a possible increase in a certain type of stroke in people ages 65 and older who had recently received one of Pfizer’s updated booster shots .

A rapid response analysis of this signal found that seniors who received a bivalent booster dose were more likely to have an ischemic stroke within the first three weeks after vaccination compared to weeks four through six.

Ischemic strokes, the most common form, are blood blockages in the brain. They are usually caused by clots.

The Vaccine Safety Datalink or VSD is a Network of large health systems across the country that provides data on vaccine safety and efficacy via electronic health records. The CDC said it has identified possible confounders in the data from the VSD that could skew the data and warrant further investigation.

Of about 550,000 seniors who received bivalent Pfizer boosters and were followed by the VSD, 130 suffered a stroke in the three weeks following the injection, according to a CDC official who spoke to CNN on condition of anonymity because they were not eligible to pass on the data . None of the 130 people died.

The number of strokes detected is relatively small, said Dr. William Schaffner, an infectious disease expert at Vanderbilt University and a member of the Covid-19 Vaccine Work Group of the CDC Advisory Committee on Immunization Practices.

“These strokes are not a confirmed adverse event at this time,” he said. “It’s like a radar system. They get a spot on the radar and have to investigate further to find out if this plane is friend or foe.”

The same safety signal was not detected with the Moderna bivalent booster, the CDC said in its release.

The agency noted that they looked for the same increase in strokes in other large collections of medical records, including those maintained by Medicare, the U.S. Department of Veterans Affairs, as well as its vaccine adverse event reporting system known as have not found VAERS.

Neither Pfizer nor other countries using the vaccine have seen an increase in this type of stroke, the agency said, and the signal has not been spotted in any other database.

The CDC says it is not recommending any change in vaccination practices at this time and that the risks of Covid-19 for older adults continue to outweigh any potential safety issues with the vaccine.

“Although the body of data currently suggests that it is very unlikely that the signal in VSD poses any real clinical risk, we believe it is important to share this information with the public. as we have done in the pastwhen one of our security surveillance systems detects a signal,” the statement said.

“CDC and FDA will continue to evaluate additional data from these and other vaccine safety systems. This data and additional analysis will be discussed in the next Meeting on January 26th 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 U.S. Food and Drug Administration (FDA) have observed similar results in numerous other surveillance systems in the U.S. and worldwide, and there is no evidence to suggest that.” It is an ischemic stroke related to the use of the companies’ COVID-19 vaccines.

“Compared to the published incidence rates of ischemic stroke in this elderly population, the companies have observed a lower number of reported ischemic strokes after vaccination with the Omicron BA.4/BA.5-adapted bivalent vaccine.”

Pfizer/BioNTech and Moderna’s bivalent boosters protect against the original strain of coronavirus and subvariants Omicron BA.4 and BA.5. Only about 50 million Americans ages 5 and older have received them since they were approved last fall, according to the CDC given.

Schaffner said he attended a briefing with members of the Covid-19 Vaccine Work Group on Thursday. He couldn’t share specific details about the briefing but said the safety signal was discussed.

His greatest realization was that the security surveillance system was working.

It’s very likely this is a false signal, he said, but it’s investigating what’s important.

“They want a surveillance system that occasionally sends false signals. If you don’t get signals, worry that you’re missing something.”

Schaffner said he would strongly advise people to get their Covid-19 booster if they haven’t already – including those 65 and older.

“Clearly, the risk of a whole range of adverse events, including hospitalizations, is much, much greater with Covid-19 than with vaccination,” he said.

He also said the signal – if genuine – could be a number factor rather than an indication that one manufacturer’s vaccine is riskier than another.

Almost two-thirds of people in the US who received an updated booster shot — 32 million — received Pfizer, compared to about 18 million Moderna shots.

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