Spontaneous Reporting to Regulatory Authorities of Suspected Adverse Drug Reactions to COVID-19 Vaccines Over Time: The Effect of Publicity

INTRODUCTION: The UK Medicines and Healthcare products Regulatory Agency (MHRA) has published frequent summaries of spontaneous reports of suspected adverse drug reactions (ADRs) (Yellow Cards) to vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The EudraVigilance database has provided similar data for the European Economic Area. OBJECTIVE: Our objective was to characterize the evolution over time of spontaneous reports of suspected ADRs to coronavirus disease 2019 (COVID-19) vaccines and to observe the effect of a publicized reaction (cerebral venous and sinus thrombosis [CVST]) on reporting rates. METHODS: We used publicly available data on reports of suspected ADRs and doses of vaccine administered, published by the MHRA, EudraVigilance, and the European Centre for Disease Prevention and Control to calculate reporting rates. RESULTS: Approximately 4814 Yellow Card reports (23 fatal) per million doses of ChAdOx1 nCoV-19 (AstraZeneca) and 2890 (13 fatal) per million doses of tozinameran (Pfizer/BioNTech) have been lodged. Between 15 March and 31 October 2021, cumulative European reports of CVST rose from 0 to 443 (183 with thrombocytopenia, 72 fatal) with ChAdOx1 nCoV-19 and from 2 to 315 (9 with thrombocytopenia, 28 fatal) with tozinameran. European cases of retinal vein occlusion and thrombosis rose from 0 to 168 with ChAdOx1 nCoV-19 and from 1 to 220 with tozinameran; four of the ChAdOx1 nCoV-19 cases were associated with thrombocytopenia. CONCLUSION: Reports of fatal adverse reactions to coronavirus vaccines are very rare. Reports of CVST have been made in relation to both vaccines. Most were submitted after the reaction had been publicized. Thrombocytopenia occurred in a minority of cases. Reports linked both vaccines to cases of retinal vein thrombosis, just four cases with thrombocytopenia. This suggests two different mechanisms of thrombosis associated with the vaccines.