Active Symptom-Based Surveillance of Adverse Events Following Immunization Among Individuals Vaccinated with ChAdOx1 nCoV-19 Coronavirus Vaccine in a Tertiary Hospital of Kerala

Background: The reports on adverse experiences following vaccination are scanty from India. It is important to know the real-world post-vaccination experience outside of clinical trial conditions. Objectives: The study aims to estimate the incidence of adverse events following immunization with the ChAdOx1 nCoV-19 coronavirus vaccine and to identify the predictors for the development of vaccine adverse events. Methods: A prospective observational study was conducted among health care workers who received the ChAdOx1 nCoV-19 coronavirus vaccine. Study participants were monitored at the site for 30min following vaccination and were followed up for 7 days after receiving the second dose, with a purpose-specific designed online surveillance form to enquire about any adverse events following vaccination. We used the Chi-squared test for categorical variables and multivariate regression analysis to identify predictors for the development of vaccine adverse effects. Results: Of 411 participants, the mean age was 30.77 +/- 12.5 years and 76.2% were females. Overall, 207 (50.4%) respondents reported at least one post-vaccination symptom receiving either dose of coronavirus vaccination. Fever (34.8%), local pain at the injection site (28.0%), tiredness (25.5%), chills (20%), myalgia (18.7%), headache (17.8%), injection site stiffness (5.4%), joint pain (4.6%) and nausea-vomiting (3.8%) were the most prevalent symptoms following the first dose. Adverse reactions reported after the second dose were milder and less frequent. Post-vaccination symptoms were more likely in the younger age group, those with comorbidity particularly, bronchial asthma, and a history of allergy to food/drugs. Conclusion: All the adverse reactions were of a minor type and non-serious. Side effects were less common in older adults (>60 years). Reactions to the second dose were lesser in intensity and frequency. Younger age, history of allergy, and comorbidities, particularly asthma, were found to be major predictors for the development of adverse events and require more watchful vaccine administration.