Effectiveness of vaccination in preventing severe SARS CoV-2 infection in South India-a hospital-based cross-sectional study

Background & objectives Establishing concrete evidence on the effect of vaccination on the severity of SARS CoV-2 infections in real-world situations is the need of the hour. This study aims to estimate the effectiveness of Covid 19 vaccines in preventing the new and severe SARS CoV-2 infections. Design Cross-sectional study Setting& Participants We did this cross-sectional study among the 4565 patients consecutive adult inpatients admitted in the Covid 19 wards of a tertiary care hospital from May 7, 2021, to October 7, 2021, during the second wave of the Covid 19 pandemic. Information on basic demographic variables, RT PCR status, vaccination status, outcome and clinical severity of illness were obtained from the electronic hospital patient records. Results Only 4% of the study participants had prior vaccination. The type of vaccine and number of doses didn’t have any protective effect against the new SARS CoV-2 infection and breakthrough infection. Fully vaccinated RTPCR positive patients had an 82% reduction in the need for ICU admission (OR 0.09; AOR 0.18, CI (0.04 to 0.8), P 0.05). Conclusion Vaccination doesn’t protect against new SARS Cov-2 infection and breakthrough infection however significant protection was documented against severe SARS Cov-2 infection. The protective effect shown by the vaccines in preventing the severe form of SARS Cov-2 infection among fully vaccinated patients was 82%. Vaccination coverage should be increased urgently to halt the impending wave of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.