A Retrospective Observational Study to Compare the Clinical and Laboratory Parameters of Patients Requiring Hospitalization during 3rd Wave vs 2nd Wave of Coronavirus Disease 2019.

Background: Following the outbreak of coronavirus in Wuhan, China in 2019, there has been multiple waves of different variants of COVID-19 throughout the world in the continuum of a pandemic. This study aims to compare different clinical and laboratory parameters of hospitalized patients in Omicron-driven 3rd wave vs Delta-driven 2nd wave in India. Materials and methods: This was a retrospective cross-sectional observational study that was done in the Department of General Medicine, Mahatma Gandhi Hospital, Dr S N Medical College, Jodhpur (Rajasthan). It included 100 patients of 3rd wave and 2nd wave respectively who were hospitalized. The primary outcome of the study was patient's survival and condition at discharge and secondary outcomes included length of hospital stay and mode of oxygenation. Results: The presence of cough, shortness of breath, and loss of taste are more common symptoms in 2nd wave vs 3rd wave with p-value being 0.0002, 0.004, and < 0.0001 respectively. The severity of illness, need for intensive care unit (ICU), and outcome in terms of discharge with oxygen or without oxygen were also statistically significant in the 2nd wave vs 3rd wave with p-value being < 0.0001 for all three variables. A total of 67% of patients were vaccinated in 3rd wave group compared to 11% in 2nd wave group (p-value < 0.0001). Comparison of laboratory parameters also revealed statistically significant results with D-dimer, quantitative C-reactive protein (CRP), normal (NL) ratio, and serum lactate being more deranged in the 2nd wave compared to the 3rd wave with p-value being < 0.05. Comparison of involvement of lung parenchyma based on computed tomography (CT) severity score revealed p-value < 0.0001 that is statistically relevant. Conclusion: Omicron-driven 3rd wave was associated with significantly less severity, less inflammatory response, and better outcome compared to Delta-driven 2nd wave. More vaccination and probably less intrinsic virulence during 3rd wave has a major role in the better outcome.