Atlanta—In an effort to be transparent, the CDC and the FDA announced that reports of ischemic stroke in recipients of Pfizer-BioNTech COVID-19 Vaccine, Bivalent reached a level to require additional investigation.

That does not mean the vaccine caused that side effect or that a change in vaccine recommendations is forthcoming, according to the agencies, which added that similar safety signals did not occur after receipt of the Moderna bivalent vaccine.

“U.S. government agencies use multiple, complementary safety monitoring systems to help detect possible safety signals for vaccines and other medical countermeasures as early as possible and to facilitate further investigation, as appropriate,” according to a press release from the CDC and FDA. “Often these safety systems detect signals that could be due to factors other than the vaccine itself.”

It is not clear yet whether the signal represents an actual concern with the vaccine or if it can be determined to be of no clinical relevance.

“Following the availability and use of the updated (bivalent) COVID-19 vaccines, CDC’s Vaccine Safety Datalink (VSD), a near real-time surveillance system, met the statistical criteria to prompt additional investigation into whether there was a safety concern for ischemic stroke in people ages 65 and older who received the Pfizer-BioNTech COVID-19 Vaccine, Bivalent,” according to the agencies. “Rapid-response investigation of the signal in the VSD raised a question of whether people 65 and older who have received the Pfizer-BioNTech COVID-19 Vaccine, Bivalent were more likely to have an ischemic stroke in the 21 days following vaccination compared with days 22-42 following vaccination.”

Public health officials added that is it important to note that, so far, no other safety systems have shown a similar signal and multiple subsequent analyses have not validated this signal. Those include:

• A large study of updated (bivalent) vaccines (from Pfizer-BioNTech and Moderna) using the Centers for Medicare and Medicaid Services database revealed no increased risk of ischemic stroke
• A preliminary study using the Veterans Affairs database did not indicate an increased risk of ischemic stroke following an updated (bivalent) vaccine
• The Vaccine Adverse Event Reporting System managed by the CDC and FDA have not seen an increase in reporting of ischemic strokes following the updated (bivalent) vaccine
• Pfizer-BioNTech’s global safety database has not indicated a signal for ischemic stroke with the updated (bivalent) vaccine
• Other countries have not observed an increased risk for ischemic stroke with updated (bivalent) vaccines.

“Although the totality of the data currently suggests that it is very unlikely that the signal in VSD represents a true clinical risk, we believe it is important to share this information with the public, as we have in the past when one of our safety monitoring systems detects a signal. CDC and FDA will continue to evaluate additional data from these and other vaccine safety systems,” the CDC said, and continues to recommend that everyone aged 6 months and older stay up to date with COVID-19 vaccination, adding that the recommendation includes individuals who are currently eligible to receive an updated (bivalent) vaccine.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.