What has been observed? The problems observed in some people vaccinated with AstraZeneca are not regular thromboses (formation of blood clots), as initially reported, but a “very atypical” phenomenon, the French Medicines Agency has said. It is about “thromboses of the large veins, atypical by their localization (cerebral in the majority, but also digestive) and usually associated with thrombocytopenia (a deficit in blood platelets) or with disorders of coagulation,” according to the ANSM. File: Britain’s Prime Minister Boris Johnson holds a vial of the AstraZeneca COVID-19 vaccine during a visit to a vaccination center at the Health and Well-being Centre in Orpington, south-east London, Monday, Feb. 15, 2021. (Jeremy Selwyn/Pool Photo via AP)