ABSTRACT
Background: There is paucity of real-world data on COVID-19 vaccine effectiveness and safety from cohort designs. The current study aimed to evaluate vaccine performance during second wave in India. It also aimed to determine adverse events of significant concern (AESCs), and to ascertain the effect of vaccination on persistent health issues in individuals post COVID-19. Methods: A cohort study was conducted from July-2021 to December-2021 in a tertiary hospital of north India. The primary outcome was vaccine-effectiveness against COVID-19. Secondary outcomes were AESCs, and persistent health issues in those receiving vaccine. Regression analyses were performed to determine risk factors. Results: In 2760 healthcare workers (HCWs) included, 1033 COVID-19 events were reported. Around 6-17% vaccine effectiveness was observed against COVID-19 occurrence. One dose-recipients were at 1.6-times increased risk of COVID-19. Prior SARS-CoV-2 infection was a strong independent protective factor against COVID-19 (aOR 0.66). Full vaccination reduced moderate-severe COVID-19 by 57%. Those with lung disease were at 2.5-times increased risk of moderate-severe COVID-19. AESCs were observed in 1.3% including one case each of myocarditis and severe hypersensitivity. Individuals with hypothyroidism were at 5-times and those receiving vaccine after recovery from COVID-19 were at 3-times higher risk of persistent health issues. Conclusion: COVID-19 vaccination reduced COVID-19 severity but offered marginal protection against occurrence. Relationship of asthma and hypothyroidism with COVID-19 outcomes necessitates focused research. Independent protection of prior SARS-CoV-2 infection was high and persistent health issues were common in individuals receiving vaccine post COVID-19. Recommendations of vaccinating those recovered from COVID-19 need further studies.