ABSTRACT
Background: During the first quarter of 2021, several European countries suspended the use of the Oxford-AstraZeneca vaccine amid reports of blood clot events and the death of a vaccinated person. This was followed by several reports of fatalities related to pulmonary embolism and other thrombotic events including thrombocytopenia which has been referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT). Aim(s): This study investigated the occurrence of thrombotic adverse events and their clinical outcomes of the three approved and most used COVID-19 vaccines namely Moderna, Pfizer and Oxford-AstraZeneca, using one of the largest spontaneous adverse events databases, namely EudraVigilance. Method(s): A retrospective descriptive analysis was conducted of spontaneous reports for Moderna, Pfizer and Oxford-AstraZeneca COVID-19 vaccines submitted to the EudraVigilance database in the period from 17 February to 14 June 2021. Result(s): There were 729,496 adverse events for the three vaccines, of which 3420 were thrombotic, mainly Oxford-AstraZeneca (n = 1988, 58 1%) followed by Pfizer (n = 1096, 32 0%) and Moderna (n = 336, 9 8%). As serious adverse events, there were 705 reports of pulmonary embolism for the three vaccines, of which 130 reports (18 4%) were for Moderna, 226 reports (32 1%) for Pfizer and 349 (49 5%) for Oxford-AstraZeneca vaccines. The occurrence of pulmonary embolism is significantly associated with a fatal outcome (p = < 0 001). Sixty-three fatalities were recorded (63/3420, 1.8%), of which Moderna (n = 6), Pfizer (n = 25) and Oxford-AstraZeneca (n = 32). Conclusion(s): Thrombotic adverse events reported for the three vaccines remains extremely rare with multiple causative factors reported elsewhere as precipitating these events. Practicing vigilance and proper clinical management for the affected vaccines, as well as continuing to report adverse events, are essential. More than 4 89 billion doses of different COVID-19 vaccines have been administered across the globe. On the basis of scientific evidence showing that benefit outweighs risk, people continue to be urged to accept the vaccination when offered.
ABSTRACT
The development of safe, effective, affordable vaccines against COVID-19 remains the cornerstone to mitigating this pandemic. Early in December 2020, multiple research groups had designed potential vaccines. From 11 March 2021, several European countries temporarily suspended the use of the Oxford-AstraZeneca vaccine amid reports of blood clot events and the death of a vaccinated person, despite the European Medicines Agency (EMA) and the World Health Organization's assurance that there was no indication that vaccination was linked. This study aimed to identify and analyse the thrombotic adverse reactions associated with the Oxford-AstraZeneca vaccine. This was a retrospective descriptive study using spontaneous reports submitted to the EudraVigilance database in the period from 17 February to 12 March 2021. There were 54,571 adverse reaction reports, of which 28 were associated with thrombotic adverse reactions. Three fatalities were related to pulmonary embolism;one fatality to thrombosis. With 17 million people having had the AstraZeneca vaccine, these are extremely rare events The EMA's Pharmacovigilance Risk Assessment Committee (18 March 2021) concluded that the vaccine was safe, effective and the benefits outweighed the risks. Conducting further analyses based on more detailed thrombotic adverse event reports, including patients' characteristics and comorbidities, may enable assessment of the causality with higher specificity.