Effect of SARS-CoV-2 Vaccination on Severity and Outcome of COVID-19 among Health-care Workers of a Tertiary Care Hospital in India

Introduction: SARS-CoV-2 vaccines decrease the risk of infection. However, data on the utility of vaccines in decreasing the severity of COVID-19 need to be evaluated. This study was carried out with the primary objective to assess the severity and clinical outcome of COVID-19 infections among unvaccinated and vaccinated health-care workers (HCWs). Methods: This was a hospital-based retrospective cohort study including all HCWs who developed microbiologically confirmed COVID-19 over 6 months from January 31, 2021, to July 31, 2021 (during the second wave of COVID-19 in India). Data were recorded through a questionnaire which included demographic details, primary location of work, history of vaccination with dates, comorbidities, severity of COVID-19, and outcome. HCWs who tested positive for SARS-CoV-2 before any dose of the COVID-19 vaccine were included in the "unvaccinated " group. Whereas HCWs who developed SARS-CoV-2 after a single or both doses of vaccine were included in the vaccinated group. The outcome and mortality among the vaccinated and unvaccinated groups were evaluated and compared. Results: The study included 500 HCWs who developed a microbiologically confirmed CVOID-19 infection. It was a predominantly middle-aged population with 247 unvaccinated and 253 vaccinated at the time of developing COVID-19. Only one-fourth of the population (26%) was working in the COVID-19 area and the source of COVID-19 to most was either a COVID-19 patient (39%) or a colleague (38%). Around 13% of the population had comorbidities with cardiovascular disease and diabetes being the most common. The majority of the patients were mild (71%) and most were treated at home in isolation (91%). Only 4% of the study population required intensive care. Among the vaccinated group, COVID-19 infection was predominantly mild and this difference was statistically significant as compared to the nonvaccinated. No difference was found in mortality among the two groups; however, the overall mortality was only 1%. Conclusions: SARS-CoV-2 vaccines reduce the severity of COVID-19 besides preventing infections and its spread. This can help in effective care of COVID-19 in home isolation without overburdening the health-care services. More studies including clinical parameters and microbiological components are required to understand the true extent of this protection of vaccines from severe forms of COVID-19.