Inpatient COVID-19 Mortality Has Reduced Over Time: Results from an Observational Cohort

Introduction: The Covid-19 pandemic in the United Kingdom has seen two waves; the first starting in March 2020 and the second in late October 2020.  It is not known whether outcomes were different in the first and second waves. Methods: The study population comprised all patients admitted to a 1,500-bed London Hospital Trust between March 2020 and January 2021, who tested positive for Covid-19 by PCR within 3-days of admissions. Primary outcome was death within 28-days of admission. Socio-demographics (age, sex, ethnicity), hypertension, diabetes, obesity, baseline physiological observations, CRP, neutrophil, chest x-ray abnormality, remdesivir and dexamethasone were incorporated as co-variates. Proportional subhazards models compared mortality risk between wave 1 and wave 2. Cox-proportional hazard model with propensity score adjustment were used to compare mortality in patients prescribed remdesivir and dexamethasone. Findings: There were 3,457 COVID-19 admissions, 2,494 hospital discharges and 619 deaths. There were notable differences in age, ethnicity, comorbidities, and admission disease severity between wave 1 and wave 2. Twenty-eight-day mortality was higher during wave 1 (25.7% versus 13.2%). Mortality risk adjusted for co-variates was significantly lower in wave 2 compared to wave 1 [adjSHR 0.41(0.30, 0.56)p<0.001]. Analysis of treatment impact did not show statistically different effects of remdesivir [HR 1.22(95%CI 0.91, 1.62),p=0.18] or dexamethasone [HR 1.31(95%CI 0.80, 2.14),p=0.29]. Interpretation: There has been substantial improvements in COVID-19 mortality in the second wave, even accounting for demographics, comorbidity, and disease severity. Neither dexamethasone nor remdesivir appeared to be key explanatory factors, although there may be unmeasured confounding present. Funding: None. Conflict of Interest: None declared by authors. Ethical Approval: This project operated under London South East Research Ethics Committee (reference 18/LO/2048) approval granted to the King’s Electronic Records Research Interface (KERRI); specific work on COVID-19 research was reviewed with expert patient input on a virtual committee with Caldicott Guardian oversight.