Lung function decline in relation to COVID-19 in the general population: a matched cohort study with pre-pandemic assessment of lung function

Objective To quantify the potential decline in dynamic lung volumes following coronavirus disease 2019 (COVID-19) in the general population. Methods A prospective matched cohort study of adult Copenhagen General Population Study (CGPS) participants with a pre-pandemic spirometry available. CGPS individuals with a positive SARS-CoV-2 polymerase chain reaction (PCR) test performed a repeat spirometry, a questionnaire regarding respiratory symptoms and a diffusing capacity test for carbon monoxide. A matched uninfected CGPS control sample was used, and simple regression and linear mixed effect models were computed to study lung function decline. Results A total of 606 were included. 92/107 (85.9%) of individuals with a positive SARS-CoV-2 PCR test experienced COVID-19 symptoms and 12 (11.2%) were hospitalized. Spirometry was performed at a median (interquartile range) of 5.6 (3.9-12.8) months after positive SARS-CoV-2 PCR test. COVID-19 was associated with an adjusted 7.3 mL (95%CI: 0.3-14.3) and 22.6 mL (95%CI: 13.1-32.0) steeper decline in annual FEV1 and FVC or a total of 113.8 and 301.3 ml lower FEV1 and FVC from baseline to follow up. Results were robust in analyses restricted to individuals not requiring hospitalization. Conclusion COVID-19 related decline of dynamic lung volumes in the general population not requiring hospitalization were small but measurable.

Early estimates of SARS-CoV-2 Omicron variant severity based on a matched cohort study, Ontario, Canada

While it is now evident that Omicron is rapidly replacing Delta, due to a combination of increased transmissibility and immune escape, it is less clear how the severity of Omicron compares to Delta. In Ontario, we sought to examine hospitalization and death associated with Omicron, as compared to matched cases infected with Delta. We conducted a matched cohort study, considering time to hospitalization or death as the outcome, and analyzed with a Cox proportional hazards model. Cases were matched on age, gender, and onset date, while vaccine doses received and time since vaccination were included as adjustment variables. We identified 6,314 Omicron cases that met eligibility criteria, of which 6,312 could be matched with at least one Delta case (N=8,875) based on age, gender, and onset date. There were 21 (0.3%) hospitalizations and 0 (0%) deaths among matched Omicron cases, compared to 116 (2.2%) hospitalizations and 7 (0.3%) deaths among matched Delta cases. The adjusted risk of hospitalization or death was 54% lower (HR=0.46, 95%CI: 0.27, 0.77) among Omicron cases compared to Delta cases. While severity may be reduced, the absolute number of hospitalizations and impact on the healthcare system could still be significant due to the increased transmissibility of Omicron.