Abstract
Background: The World Health Organization had proclaimed the outbreak of the novel coronavirus (COVID-19) as a worldwide pandemic on March 11, 2020. Immunization against the disease was the need of the hour to curtail the spread of COVID-19 pandemic. Two vaccines manufactured in India were approved for emergency use authorization initially. They are ChAdox1CoV-19 vaccine – CoviShield and Covaxin.

Aims and objectives: This study aimed at assessing the occurrence of adverse effects following immunization (AEFI) among individuals who received the CoviShield vaccine. The objective of this research was to evaluate the type of AEFI among vaccinated beneficiaries and to determine the factors contributing to the development of AEFI.

Materials and Methods: A cross-sectional study was done at a teaching hospital in Kerala. All beneficiaries who were administered CoviShield vaccine during the study period, that is, from January 2021 to June 2022 were incorporated in the study. Data regarding AEFI were collected from all vaccinated individuals by direct or telephonic enquiry.

Results: The incidence rate of AEFI is 4.5/1000 doses (111/24925 doses). The reporting of AEFI was high among age group of 20–30 years and commonly seen in males (97.3%). The most common AEFI reported with CoviShield vaccine were fever (63%), myalgia (51%), and headache (40%). AEFI were seen commonly after administration of first dose (94%). Only 7 cases (6.3%) of serious AEFI were reported which included death, autoimmune encephalitis, Bell’s palsy, hypotension, and hypersensitivity reactions. There was no significant association between age and type of AEFI (P > 0.05) and dose of vaccine and type of AEFI (P > 0.05).

Conclusion: The immunization with CoviShield vaccine is safe among adults (>18 years) with lesser incidence of serious adverse effects. Higher incidence of AEFI is witnessed after administration of first dose and it was commonly seen in males.

Key words: AEFI; CoviShield; Dose; Immunization; Vaccine