Effect of Vaccination on COVID-19 Severity and Outcome: A Comparative Study in a Tertiary Care Hospital

Vaccination is an important aspect of preventing/decreasing the severity of any viral disease including severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). This disease being very new in the experience of mankind has very little data on the effect of vaccination on the severity of this disease. We conducted this study with the primary objective to assess the severity and clinical outcome of COVID-19 infections among nonvaccinated and vaccinated individuals.

This was a hospital-based retrospective cohort study including all individuals developing microbiologically confirmed COVID-19 over 5 months from February to 31^st July 2021. A questionnaire was used to acquire demographic details, history of vaccination with dates, severity of COVID-19 infection, comorbidities, and outcome. Patients found positive microbiologically for SARS-CoV-2 before any dose of its vaccine were considered nonvaccinated, while patients developing SARS-CoV-2 infection even after a single dose or both doses of vaccine were considered "vaccinated." The outcome and mortality among the vaccinated and nonvaccinated patients were evaluated and compared.

The study included 2,879 patients, but complete data were obtained only from 1,500 patients. A total of 1,500 patients were analyzed, out of which 880 are male and 620 are female. The severity of the disease was categorized into mild, moderate, and severe in the age-group of <60 years and >60 years with urban (1051, 70.07%) and rural (449, 29.93%) populations. A total number of recovered patients (n = 245), died patients (n = 215) in the age-group of >60 years while the total recovered patients (n = 823) and dead patients (n = 217) in the age-group <60 years with p = 0.001. Total vaccinated patients in the age-group >60 years (n = 204) and not vaccinated (n = 256) while in the age-group of <60 years total vaccinated n = 229 and not vaccinated n = 811. The outcome of disease in the age-group of >60 years in nonvaccinated 50% recovered and 50% died during the course of illness while in the vaccinated 57.3% recoverd and 42% died p-value 0.14, while in the age-group of <60 years recovery in nonvaccinated 77.6% and death in nonvaccinated was 27.32% while in vaccinated patients 82.28% were recovered and 15% died with significant p-value 0.04. Disease outcome was not found significantly associated with a number of doses with p-values of 0.84 and 0.507 in the age-group of >60 years and <60 years, respectively. A total number of 56 patients received Covaxin and 377 patients received Covishield and disease outcome was not found significantly associated with the type of vaccine.

Vaccination against COVID-19 was significantly effective in terms of hospitalization and disease severity. Vaccinated persons were less among patients with COVID-19 hospitalization and with severe disease progressing to death. These findings indicate vaccination is helpful in reducing the development of severe COVID-19 infection as compared to nonvaccinated status.