Covid-19 vaccine blood clot cartoon March 31, 2021 by chrismadden Covid-19 blood clot cartoon. The AstraZeneca Covid-19 vaccine has been rumoured to cause blood clots (with little evidence). The cartoon shows someone (an anti-vaxxer) reacting to this. First published in the Spectator, March 2021. Drawn: March 2021 Cartoon reference number: a920