New Study Reports Small Increased Risk of Strokes in Seniors from Covid-19 and Flu Vaccines
A new study conducted by experts at the US Food and Drug Administration (FDA) suggests that vaccines for Covid-19 and influenza may slightly increase the risk of strokes caused by blood clots in the brains of seniors, particularly when the vaccines are given simultaneously and to adults over the age of 85. This is the second study to find an elevated risk of stroke in seniors after receiving both Covid-19 and flu vaccinations together.
The study analyzed data from Medicare claims and detected a safety signal indicating a small and uncertain risk of strokes in older adults who received Pfizer’s bivalent Covid-19 vaccine and a high-dose or adjuvanted flu shot on the same day. The FDA’s broader investigation into strokes after vaccination among seniors on Medicare revealed that the risk is minimal, with approximately 3 strokes or transient ischemic attacks occurring for every 100,000 doses given. The study also found that the increased risk may be primarily associated with high-dose or adjuvanted flu vaccines, which are designed to stimulate a stronger immune response.
Further analysis of the Medicare claims data showed a slightly increased risk of stroke in adults aged 65 and older who received only a high-dose flu shot. However, in absolute terms, the additional risk amounted to only 1-2 strokes for every 100,000 doses. Experts emphasize that the overall risk is minuscule compared to the risk of severe outcomes from Covid-19 or influenza infections, especially for those over the age of 85.
Despite these findings, at least five other recent studies have not found any additional risk of stroke after vaccination for Covid-19, influenza, or both. The CDC’s Advisory Committee on Immunization Practices stated that the available data do not provide clear and consistent evidence of a safety problem for ischemic stroke related to bivalent mRNA Covid-19 vaccines.
Dr. William Schaffner, an infectious disease expert at Vanderbilt University, reassures the public that the benefits of vaccination against Covid-19 and influenza far outweigh the potential risks. He notes that the risk of serious disease associated with both viruses is much greater than the possible increased risk associated with vaccines. Dr. Schaffner suggests considering getting the shots at different times if individuals are concerned about potential interactions between the vaccines.
The FDA study is observational and cannot prove cause and effect; it can only show associations. The research was posted as a preprint and has not undergone peer review by independent experts or publication in a medical journal. The authors of the study caution that their findings should be interpreted with caution and hope for further investigation through robust epidemiological studies.
In a separate investigation, the FDA found a small and tenuous link between seizures in children aged 2 to 5 and Covid-19 vaccination. However, this association disappeared when compared to background rates of seizures reported in US children in 2022.
Health experts urge the public not to be deterred by these findings and emphasize that the benefits of vaccination against Covid-19 and influenza far outweigh the potential risks. The medical community continues to encourage everyone to get vaccinated to protect themselves and others from severe illness and complications.