On Apr. 7, 2021, the COVID-19 subcommittee of the WHO Global Advisory Committee on Vaccine Safety (GACVS) announed that they had reviewed reports of rare cases of blood clots with low platelets following vaccination with the AstraZeneca COVID-19 vaccine (including Covishield) since their onset.

Based on current information, a causal relationship between the vaccine and the occurrence of blood clots with low platelets was considered plausible but was not confirmed. Specialised studies were needed to fully understand the potential relationship between vaccination and possible risk factors.