Federal Officials Detected Pfizer Bivalent Booster Stroke Signal in November 2022

Federal health officials detected a statistically significant safety signal in November 2022 linking the Pfizer-BioNTech bivalent booster to ischemic stroke in adults 65 and older. The signal kept showing up week after week. Reports of strokes piled up in the Vaccine Adverse Event Reporting System.

By February 2023, internal records showed 226 stroke cases reported. Yet the FDA and CDC continued to recommend the bivalent booster for adults 65 and older after the safety signal was detected. CDC officials acknowledged the "WH and HHS intense push to increase uptake of the booster" was driving the messaging.

“no change is recommended in COVID-19 vaccination practice.”

“— January 2023 FDA website notice Contractors were running the "Stroke Project" to investigate the risk. The investigations continued through at least September 2025. Sen. Ron Johnson's office compared reported death rates across vaccines. COVID injections produced 25.5 deaths per million doses reported. The flu vaccine produced 0.46 deaths per million doses reported. That equates to a 55-fold increase in reported deaths per dose for COVID injections compared to the flu vaccine. FDA officials kept telling Americans, including patients with diagnosed injection injuries, that no safety signals existed. @MarioNawfal reported the details from an investigation led by Sen. Ron Johnson. The findings center on events that began in late 2022 and extended into 2025, more than two years after the initial detection of the signal in November 2022. The safety signal first appeared in November 2022. Internal concern mounted through early 2023 as stroke reports accumulated. Public communications in January 2023 acknowledged a signal existed while stressing no change to vaccination practice. By February 2023 the internal count stood at 226 reported stroke cases. The "Stroke Project" operated by contractors ran in parallel to the public messaging. That work extended at least until September 2025. Throughout the period the FDA and CDC maintained their recommendation for adults 65 and older. CDC officials internally cited the "WH and HHS intense push to increase uptake of the booster" as a factor shaping communications. Language in a draft plan was revised from "moderately elevated" to "slightly elevated.”