A new analysis conducted by the Food and Drug Administration (FDA) has identified a possible link between receiving the Pfizer or Moderna Covid booster vaccines alongside a high-dose flu shot and a modest increase in stroke risk. The risk was particularly evident in adults over the age of 85. It is worth noting that this association may be with the flu vaccine alone, rather than in conjunction with the Covid shots. Nevertheless, the FDA report emphasizes that the overall risk is still minimal.
According to the analysis, for every 100,000 doses administered, there were approximately three strokes or stroke-like events known as transient ischemic attacks. In comparison, the death rate from Covid among individuals aged over 85 in 2022 was 1,224 per 100,000. This highlights the importance of vaccination, despite the small associated risk.
This analysis is the second one conducted by health officials to indicate a possible connection between strokes and seniors who received the combined seasonal vaccines. However, it is crucial to acknowledge that both studies were observational and cannot establish a causal link, only an association.
The analysis included nearly 5.4 million Medicare beneficiaries aged 65 and older. Researchers specifically examined the correlation between receiving the flu shot and either the Moderna or Pfizer Covid booster on the same day, and the incidence of non-hemorrhagic stroke (NHS) and transient ischemic attack (TIA). Both of these stroke types are caused by blood clots that obstruct blood flow to the brain.
The study revealed that individuals who received a high-dose flu shot and the Moderna bivalent booster had a 35 percent increased risk of experiencing a transient or "mini" stroke. Meanwhile, those who received a flu shot alongside the bivalent Pfizer booster faced a 20 percent higher risk.
When analyzing the potential link between stroke and flu vaccines alone among over 6.9 million seniors, the study found that the flu shot alone increased stroke risk by approximately nine percent, a small but noteworthy increase. Researchers speculated that since no statistically significant link was identified between stroke and Covid boosters alone, the flu vaccine might be the driving factor behind the increased stroke risk.
Although the absolute risk of suffering a stroke following a high-dose flu shot and either a Pfizer or Moderna booster was low, with an additional 3.1 to 3.3 strokes per 100,000 doses administered, it is worthwhile to note that the risk of stroke is significantly higher following a Covid infection itself.
A study published in Nature Medicine in 2022 reported that individuals who survived the initial 30 days of a Covid infection had a 52 percent higher risk of experiencing a stroke and a 49 percent increased risk of a "mini-stroke". This highlights the importance of vaccine protection against Covid, considering the elevated stroke risk associated with the infection itself.