Prevalence, severity, and risk factor of breakthrough infection after vaccination with either the Covaxin or the Covishield among healthcare workers: A nationwide cross-sectional study.

Background and Aims: The coronavirus disease-2019 (COVID-19) pandemic has grappled the entire globe since the beginning of 2020. In India, two vaccines were released in January 2021, the Covaxin® and the Covishield™. However, despite vaccination, many breakthrough infections were reported during the second wave in India. The present cross-sectional study aimed to find out prevalence, severity, and associated risk factors of breakthrough infection among healthcare workers (HCWs) vaccinated against COVID-19.

Material and Methods: After ethical approval and CTRI registration, a validated questionnaire was circulated as Google form-based survey to HCWs across the nation through e-mail over 3 weeks. Biweekly reminders were sent to nonresponders till the desired sample size was attained, after which the survey was closed, and responses were charted. Data obtained from the responses were collated and analyzed.

Results: A total of 1096 HCWs responded to the survey (54.8% response rate) and 23.36% had breakthrough infection. The severity of infection was more in the 30-50 years age group (P = 0.0170) and doctors belonging to clinical branches (P = 0.0005). The point estimate for effectiveness in preventing infection was significantly better with Covishield™ (78.5% vs. 72.4%) (P = 0.0260). Nearly all those who were infected after vaccination thought that vaccination decreased disease severity.

Conclusion: Breakthrough COVID-19 infection still occurred after vaccination though the prevalence of severe infection was low. Covishield™ performed significantly better than Covaxin® in terms of preventing the disease. Clinical branches of medicine were found at a higher risk and younger HCWs or those with comorbidities had a higher severity of the disease.