Clinical Comparison of COVID Waves 2-5. An Inpatient Retrospective Comparative Analysis From Karachi, Pakistan.

Background: Each coronavirus disease 2019 (COVID-19) wave is unique in its clinical presentation and outcome. In this study, we compared the clinical characteristics and outcomes of COVID waves 2-5 in inpatient settings.

Methods: A retrospective study was conducted at the Sindh Infectious Diseases Hospital and Research Center on adult patients who were admitted with a positive COVID polymerase chain reaction from July 2020 to March 2022. SPSS 26 was used to analyze the data.

Results: A total of 3190 COVID-19 patients were admitted. Wave 2 had the highest percentage of discharges compared with mortality (81%; = .0001). Cytokine release syndrome was most common in wave 3 (32.7%; = .0001). Severe COVID on admission was predominant in wave 4 (79.4%; = .0001), with the highest rates of intubation (27.1%; = .0001), septic shock (24.3%; = .0001), and disease progression (50.8%; = .0001). In wave 5, the majority were elderly (median age, 68 years) and had mild COVID (22.4%; = .0001), most had comorbidities (84.6%; = .0001), and the ratio of acute kidney injury was high (29.2%; = .0001). Mortality was lowest in wave 2 (18.9%; = .0001) and highest in wave 4 (42.5%; = .0001; odds ratio, 3.18; 95% CI, 2.6-3.8; compared with wave 2).

Conclusions: Each wave had some unique characteristics compared with other waves, with wave 4, driven by the Delta variant, being the deadliest one in terms of disease severity and outcomes.