Comparison of Clinical Characteristics and Outcome of COVID-19 Patients Between the 4th and 5th Wave in a Tertiary Care Hospital in Karachi, Pakistan

Objective: To compare the clinical parameters of 4th and 5th COVID waves in Karachi, Pakistan. Study Design: Descriptive study. Place and Duration of the Study: PNS Shifa Hospital, Karachi, from July 2021 to February 2022. Methodology: All patients with COVID-19 in PNS Shifa Hospital were included in the study. The patients were divided into two groups, those who had COVID-19 during the 4th wave, and others who had it during the 5th wave. The patients' demographic details, comorbidities, vaccination status, initial presentation, the severity of disease, clinical progress, and final disposal from the hospital were noted. A comparison of severity, length of hospital stays, and mortality was made between the groups. Results: There were 747 patients admitted during the Delta variant-dominated 4th wave of COVID-19, and 490 patients during the 5th wave, dominated by the Omicron variant. A vast majority of fifth-wave patients had the mild disease (87.35% vs. 49.39%), with significantly lower critical patients (2.04% vs. 7.09%). Vaccination was effective against both the Delta and the Omicron variant of the SARS-CoV-2 virus. The mean length of stay in the hospital for patients was significantly lesser (p < 0.001) during the 5th wave as compared to the 4th wave (6.43 & PLUSMN; 3.37 vs. 9.56 & PLUSMN; 5.45 days). The mortality rate was 7.09% among patients admitted in the 4th wave and 2.04% in the 5th wave. This difference was statistically significant (p < 0.001). Conclusion: The severity of disease, length of hospital stays, and mortality were higher in the Delta variant-dominated 4th wave of COVID-19 as compared to the Omicron variant-dominated 5th wave in Pakistan. The vaccination was effective against both the Delta and the Omicron variant of COVID 19, as the mortality rate among the vaccinated patients during the two waves was not signifi-cantly different.