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

## TL;DR

This study compares the clinical features and outcomes of four COVID-19 waves in hospitalized patients in Karachi, Pakistan, finding that the Delta variant-driven fourth wave was the most severe.

## Contribution

The study provides a detailed clinical comparison of multiple successive COVID-19 waves in a single region, highlighting the increased severity of the Delta variant wave.

## Key findings

- Wave 4 had the highest rates of severe disease, intubation, septic shock, and mortality.
- Wave 2 had the highest discharge rate and lowest mortality.
- Wave 5 was characterized by older patients with mild disease and high rates of comorbidities and kidney injury.

## Abstract

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.

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.

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

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.