An analysis of causality assessed serious and severe adverse events following COVID-19 vaccines administered from January 2021 to September 2022 in India

Background: Vaccine safety surveillance is one of the important elements of immunization program. Causality assessment of adverse events and dissemination of their results are equally important to ensure quality of vaccines and confidence in immunization program. Research design and methods: All types of AEFIs are reported through national AEFI surveillance program that is a passive surveillance system. An analysis of causally assessed serious and severe adverse events following COVID-19 vaccines from January 2021 to September 2022 was conducted. These AEFIs are classified according to WHO’s AEFI causality assessment protocol. A descriptive statistic across each category is being presented. Results: Overall, causality assessment data of 2713 serious/severe AEFIs following COVID-19 vaccines was available for the study. Half of the serious/severe AEFIs were found to be coincidental and 15% were classified as vaccine-product-related reactions. There were 42 cases of thrombosis and thrombocytopenia syndrome and 12 cases of deep vein thrombosis. The proportion of COVID-19 infection among the total serious/severe AEFIs was 7%. Conclusion: Causality assessment of AEFIs played key role in ensuring quality of the vaccination program. The proportion of the key serious events including TTS and GBS were rare and immunization program-related errors were negligible.