Sleep Me

CDC and FDA Acknowledge Possible Safety Signal With Pfizer COVID Booster Vaccine

On January 13, the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) announced a possible safety signal associated with the Pfizer-BioNTech COVID-19 bivalent booster vaccine.[0] The Vaccine Safety Datalink (VSD), a near real-time vaccine surveillance system that includes 13 healthcare sites from across the country, identified a signal that raised a question on whether adults 65 years and older were at higher risk of ischemic stroke in days one to 21 following vaccination compared to 22 to 42 days after receiving the booster shot.[0]

The CDC and FDA acknowledged that this signal does not necessarily indicate a true clinical risk and that other systems, such as the Centers for Medicare and Medicaid Services database, have not shown an increased risk of ischemic stroke following vaccination with the Pfizer or Moderna bivalents.[1] No other surveillance systems have reported a similar signal, nor have any analyses or studies validated it.[2]

A stroke caused by a lack of blood flow to the brain, either partially or completely blocked by a clot or other obstruction, is known as an ischemic stroke.[3] According to the Washington Post, the VSD discovered that out of the total population of around 550,000 individuals who were 65 years and over, 130 suffered from a stroke within three weeks of receiving the vaccine.[3] No one who had a stroke passed away.[4]

A review of medical records at one site that saw 24 ischemic stroke cases in the three weeks following Pfizer vaccination showed that most of the people who experienced a stroke had an influenza vaccine administered on the same day as the COVID-19 vaccine.[4] In addition, analysis of a small sampling of older adults showed that three people experienced a stroke after receiving the Pfizer booster and a standard dose flu vaccine on the same day, compared to 40 people who received the Pfizer booster and a high-dose or adjuvant flu vaccine on the same day and 60 older adults who only received the COVID booster.[5]

The CDC and FDA have not changed their recommendations for COVID vaccination and urge everyone 6 months or older to stay up to date on their vaccines, including through use of the booster shots.[2] They suggest it’s unlikely the VSD signal indicates a genuine risk.[3]

The announcement has led to a variety of responses, with some people, such as Dr. Simone Gold and Robert F. Kennedy Jr.

0. “Pfizer’s Bivalent Booster Is Not Linked to Increased Stroke Risk” Verywell Health, 19 Jan. 2023,

1. “Europe, Israel Say No Signs Updated Pfizer Shot Linked to Stroke” The Epoch Times, 20 Jan. 2023,

2. “CDC Investigating Potential—But ‘Unlikely’—Link Between Pfizer Booster and Stroke Risk”, 19 Jan. 2023,

3. “FDA and CDC Alerts to Possible Stroke Risk in Older Adults After Receiving COVID Booster | HealthNews”, 25 Jan. 2023,

4. “Social Media Posts Twist Meaning of CDC, FDA Disclosure on Bivalent Booster”, 20 Jan. 2023,

5. “Stroke After Pfizer Booster May Be Connected to Flu Vaccine: Officials” The Epoch Times, 26 Jan. 2023,

Sleep Me