People with rare blood clots after a COVID-19 jab share an uncommon immune response
Some who get AstraZeneca’s or Johnson & Johnson’s shots make antibodies that spark clots
![blood clot](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2021/04/041621_eg_bloodclot_feat.jpg?fit=1030%2C580&ssl=1)
Antibodies that bind to a protein called platelet factor 4 may be behind rare, but dangerous, blood clots (one illustrated) that develop in some people vaccinated with AstraZeneca’s or Johnson & Johnson’s COVID-19 vaccines.
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