Stimulated Reporting of Adverse Events Following Immunization with COVID-19 Vaccines.

In India, up until December 2021, Covishield and Covaxin vaccines against COVID-19 were being used for mass vaccination programs. In view of the urgency of fighting the ongoing pandemic, many vaccines have been granted emergency use approval while phase 2/3 clinical trials were still underway. Even for vaccines that have completed phase 3 trials, safety data may not be comprehensive. This retrospective observational study was conducted at a designated Regional Training Centre for Pharmacovigilance cum Adverse Drug Reaction Monitoring Centre (AMC) under the Pharmacovigilance Programme of India. The data sources were stimulated spontaneous reports of Adverse Events Following Immunization (AEFI) due to the COVID-19 vaccines from 10 January to 31 December 2021. A total of 51,010 COVID vaccine doses were administered during the study period. There were 330 AEFI reported (AEFI rate: 0.65%). Six AEFI were serious events among which three were Adverse Events of Special Interest. The majority of the AEFI were systemic, reported after the first dose, and with an onset between 1 and 24 h after vaccination. On comparing Covishield and Covaxin, there were no statistically significant differences in the AEFI reported with either vaccine in terms of gender, seriousness, lag period, duration, recovery, causality, treatment received for AEFI, presence of co-morbidity, or history of COVID-19 infection. Overall, the rates of AEFI was uncommon, and serious AEFI were rare with both Covishield and Covaxin, with a higher rate after the first dose. Whether immunological tolerance or allayed anxiety was responsible for the lower AEFI risk with the second dose remains to be investigated.