Health officials say the Covid vaccine may be associated with a small increase in the risk of stroke when given alongside a high-dose flu shot.
A new analysis from the Food and Drug Administration found the link was clearest in adults over 85 and only applied to the bivalent Covid booster vaccines from Pfizer and Moderna.
The FDA said the risk could come from the flu vaccine alone and be completely independent of the Covid vaccinations. Regardless, the report says the risk is still very low.
For every 100,000 doses administered, there were about three strokes or stroke-like events, called transient ischemic attacks.
By comparison, in 2022 the death rate from Covid among those over 85 was 1,224 per 100,000, with US health experts saying vaccination still outweighs the small risk.
It is the second analysis by health officials to suggest a possible link to strokes and seniors following the combination of seasonal vaccines.
Meanwhile, a separate analysis from the FDA found a slight increase in seizure frequency following Covid vaccinations in children ages two to five.
Health officials say the Covid vaccine may be associated with a small increase in the risk of stroke when given alongside a high-dose flu shot
The papers were posted online last weekand have not yet been reviewed for publication in a scientific journal. Vaccine safety experts said the trials were well conducted.
Both studies were observational, meaning they could not prove a causal relationship, but only a connection.
In the first analysis, FDA officials analyzed the medical claims of nearly 5.4 million Americans aged 65 and older who were enrolled in the government’s Medicare health insurance program.
In particular, the researchers examined the associations between the high-dose flu vaccination specifically for seniors and the same-day bivalent Covid booster from Moderna or Pfizer and the incidence of non-hemorrhagic strokes (NHS) and transient ischemic attacks (TIA).
Both types of strokes are caused by a blood clot that blocks blood flow to the brain.
The group that received a high-dose flu shot and Moderna’s bivalent booster shot had a 35 percent increased risk of a transient or “mini” stroke.
The group that received a flu shot and Pfizer’s bivalent booster shot had a 20 percent increased risk.
Further analysis of the link between stroke and flu vaccinations alone among more than 6.9 million seniors found that vaccination alone increased their risk of stroke by about nine percent, a small but significant increase.
Since researchers were unable to find a statistically significant association between stroke and Covid booster shots, this finding suggested that it may have been the flu vaccine alone that increased the risk of stroke.
Still, the absolute risk of having a stroke after receiving both a high-dose flu shot and a bivalent booster shot from Pfizer or Moderna was low for both.
In absolute numbers, there were an additional 3.1 strokes per 100,000 doses following the Pfizer and flu vaccinations and 3.3 strokes per 100,000 doses following the flu and Moderna vaccinations.
The risk of suffering a stroke after a Covid infection is far higher than after a booster vaccination.
A 2022 study in the journal Natural medicine reported that people who survived the first 30 days of Covid infection had a 52 percent increased risk of having a stroke, as well as a 49 percent increased risk of a “mini-stroke.”
In the second analysis In a study conducted by the FDA, researchers found a very weak association between seizures in children ages two to five and older versions of the Pfizer and Moderna vaccines.
They examined health data from more than 4.1 million American children ages six months to 17 years who had received the vaccines through April 2023. At this time, these types of monovalent vaccines have been removed from the FDA’s list of approved vaccinations and replaced with the updated bivalent varieties.
Children aged two to five had a slightly higher risk of seizures after a Covid vaccination compared to background seizure rates in the general population in 2020, when overall infectious disease rates were lower due to social distancing.
But a hint that the vaccinations triggered seizures disappeared when researchers compared it to rates in 2022, when infections recurred in children.
According to the authors of the study, the connection between cramps and injections should be treated with caution.
Most of these attacks were associated with fever, which was not unexpected since many vaccines cause fever in children, an indication that they have boosted the immune system.