Researchers from Kaiser Permanente have found that there is a heightened risk of stroke for individuals under the age of 65 who receive a flu shot and the Pfizer COVID-19 vaccine on the same day. In the study, scientists identified 373 strokes in patients in the 42 days after receiving bivalent vaccination; after 42 days, 1511 strokes were reported.
Meanwhile, researchers from the Food and Drug Administration (FDA) have admitted to identifying an elevated risk of stroke for elderly individuals who receive the Pfizer or Moderna vaccines at the same time as the flu vaccine. The finding came from a self-controlled case series involving Medicare beneficiaries who received both vaccines.
They found that people aged 85 and older who received the Pfizer vaccine with their flu shot had higher risks of non-hemorrhagic stroke and transient ischemic attacks, while the elevated risk for those who received the Moderna jab was seen in those aged 65 to 74. Both types of strokes seen in the study are caused by blood clots that block the flow of blood to the brain.
All recipients aged 65 and older experienced a higher risk of non-hemorrhagic stroke 22 to 42 days after receiving a flu and Pfizer COVID vaccine combo; a higher risk of transient ischemic attack was seen in the first 21 days for those who received the flu vaccine and Moderna COVID-19 vaccine combination.
These results are being blamed largely on the high-dose flu vaccine that the patients who were studied received, which is formulated to rev up their immune system. Known as Fluzone, it contains quadruple the flu protection provided by a normal flu jab.
One high-ranking FDA official, Dr. Peter Marks, told a conference that he believes the flu, COVID-19 and RSV vaccines should be spaced out to reduce the risk of adverse events. He noted: “Oftentimes, we suggest if you want to minimize the chance of interactions and minimize confusing side effects from one with another, you wait about two weeks between the vaccines.”
Researchers in Australia have reached a similar conclusion. They note that more adults have reported experiencing negative side effects after getting a flu vaccine and Pfizer’s COVID-19 vaccine at the same time than those that are reported after receiving either of these vaccines on their own.
COVID-19 vaccines can raise blood pressure
Although it is not fully clear how a vaccine raises the risk of stroke, studies have demonstrated an increase in blood pressure after getting a COVID-19 shot, which forces the heart to work harder than usual. This stress can damage the inner lining of blood vessels and cause arteries to narrow, which fosters the development of clots. Another risk of the vaccine is the potential to spur an abnormal immune response that results in severe inflammation that blocks the flow of blood to the brain.
On top of the risk of stroke, another concern is the possibility of one vaccine impacting the response of another. For example, one study showed that vaccines that are co-administered create lower levels of antibodies, which means recipients are not getting the full benefits.
It is worth noting that some studies have found that receiving the flu and COVID-19 vaccines simultaneously does not appear to raise stroke risk. However, researchers have acknowledged that more studies are needed to reach a more definitive conclusion about this connection and what may be causing it.
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