The risk of a stroke was more prevalent for older adults who received a flu and bivalent COVID-19 vaccine within six weeks of the other in fall 2022, according to a preprint of research conducted by the FDA and CMS.
Researchers evaluated the stroke risk among more than 5 million Medicare beneficiaries aged 65 and older. They found that, between Aug. 31 and Nov. 6, 2022, those who received a bivalent COVID-19 shot and a high-dose flu vaccine had a slightly higher stroke risk than those who were only vaccinated for COVID-19.
There was not an increased risk of stroke among older adults who only received a bivalent COVID-19 shot, according to the study that is waiting on peer review.
Those who received Pfizer's COVID-19 vaccine and a flu vaccine saw a 20% increase in the risk of transient ischemic stroke, and those who got a Moderna COVID-19 vaccine and flu shot saw a 35% increased risk.
This outcome is more likely to be tied to the influenza shot, the researchers concluded: "The observed risk of stroke in the concomitant subgroup was likely driven by influenza vaccination alone rather than concomitant administration [a COVID-19 vaccine administration]."