Abstract
Objectives: Several cases of unusual thrombotic events with thrombocytopenia were reported in several countries, in association with AstraZeneca's COVID-19 vaccine. The European medicines agency conducted a detailed review and concluded that there was no evidence to suggest an association of thrombotic events with the use of COVID-19 vaccine AstraZeneca.Methods: King Abdulaziz Medical City is a 1500 bed tertiary care hospital in Riyadh, Saudi Arabia; this study describes spontaneously reported vaccine adverse effects received through the hospital's internal electronic safety reporting system from December 2020 to 13 April 2021.We assessed each report for causality association utilizing the world health organization's (WHO) causality assessment of an adverse event following immunization (AEFI) classification 2nd Edition 2019.Results: The majority of the reported events were mild to moderate, there were five serious events, one reported cardiac arrest, two cerebral venous sinus thrombosis, and two pulmonary embolism. Clinical and laboratory summary of the five patients are presented in detail.Conclusions: Efforts of pharmacovigilance in mediating the rare risk of thrombosis associated with COVID-19 vaccine are crucial in providing awareness on the possible risk factors and signs/symptoms that should raise red flags.