AstraZeneca’s and Janssen shots make antibodies that create blood clots

Evidence is building that an uncommon immune response is behind dangerous, but incredibly rare, blood clots associated with some covid-19 vaccines. But the good news is that there is a test doctors can use to identify it and get patients the right care.

A small number of people out of the millions vaccinated with AstraZeneca’s or Johnson & Johnson’s (Janssen) covid-19 shots have developed severe blood clots, such as ones in the sinuses that drain blood from the brain (SN: 4/7/21; 4/13/21). A few have died.

Studies suggest that some inoculated people develop an immune response that attacks a protein called platelet factor 4 or PF4, which makes platelets form clots. Those platelets get used up before the body can make more. So these patients wind up with both the rare clots and low levels of blood platelets.

Full story at ScienceNews.