Surveillance on Adverse Events Following COVISHIELD (ChAdOx1 nCoV-19) vaccination in Goa, India: An Observational Study.

Background: COVISHIELD, ChAdOx1 nCoV- 19 Corona Virus Vaccine was granted emergency use authorization (EUA) as the first vaccine in India in January 2021. Knowing what to anticipate after vaccination will reduce vaccine hesitancy in the public. This study aimed to identify and measure the adverse events following COVID-19 vaccination.

Materials and methods: A cross-sectional observational study was conducted at Goa Medical College, starting on February 21 till May 23, 2021. A total of 418 people were enrolled. We collected the data using the Microsoft Form and analyzed using Microsoft Excel and R-program.

Results: Of the 418 vaccine recipients, the incidence rate of AEFI (Adverse Events Following Immunization) was 54.31%. Fever, fatigue, and headache were the most commonly reported systemic AEFIs. Among these, 54.7% of AEFI were mild, 42.38% were of the moderate category, and only 2.96% were of grade 3 severity. None of the AEFIs were severe enough for hospitalization. Most of them developed symptoms within 24 hours of the first dose. Complete recovery from AEFIs took a median time of 24 hours.

Conclusion: Most of our study findings were consistent with the phase 1, 2/3 trials findings of Oxford-AstraZeneca's ChAdOx1 vaccine. The AEFI symptoms were considered immune reactions to the vaccine. The AEFIs were more common among younger individuals and females. The chance of missing a serious adverse event like a thromboembolic phenomenon cannot be ruled out. We observed low AEFI rates with COVISHIELD in the Indian population compared to Oxford- AstraZeneca's ChAdOx1 vaccine in the UK-based population, which can be explained by preexisting immunity against adenovirus in the Indian population. However, based on the study findings, we may interpret that the COVISHIELD, Serum Institute of India, carries a good safety profile overall.