There may be an explanation for the rare but serious blood clots reported among some people who received AstraZeneca's COVID-19 vaccine.
Researchers believe the blood clot occurrences are similar to heparin-induced thrombocytopenia (HIT), in which heparin triggers the immune system to produce antibodies that activate platelets. Drugs other than heparin can cause clotting disorders that strongly resemble HIT and, according to researchers, in rare cases, the AstraZeneca vaccine may be another such trigger.
Four previously healthy individuals who had received the AstraZeneca shots and developed life-threatening clots had the same kind of antibodies that activate platelets and initiate clotting in HIT, according to researchers. Twenty individuals who received the vaccine but did not develop clots did not have these antibodies.
SOURCE: Medscape March 31, 2021