The meta-analysis searched PubMed for case-control studies published from January 1 through April 22, 2020. It included 33 observational studies involving 16,003 adults, of whom 54% were male and 1,724 had diabetes; the mean age was 52.6 ± 17.4 years. Mortality was the outcome in studies comparing survival and death, while other severity outcomes included invasive ventilation and intensive care unit admission.