People who got vaccinated by AstraZeneca’s or Johnson & Johnson’s Covid-19 shots make antibodies that spark clots. The figure above is about antibodies that bind to proteins called platelet factor 4 may be behind rare, but dangerous blood clots. On the positive side, there is a test doctors can use to identify it and get patients the right care. Of the millions vaccinated with the AstraZeneca’s or Johnson & Johnson’s Covid-19 vaccines a small number of people have developed severe blood clots, such as ones in the sinuses that drain blood from the brain and 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. Currently, health care workers can test for antibodies that recognize PF4. And if a patient tests positive, there are many other anticoagulants other than heparin that clinicians can use for treatment. I found this article interesting because of the different reactions that people having to specific vaccines.