Table 2 shows the odds ratios (ORs) and 95% confidence intervals (CIs) for the studied parameters. We found that the neutrophil count, lymphocyte count, serum level of CRP, D-dimer and ferritin, SpO2%, and respiratory rate were significant risk variables for COVID-19 severity. Interestingly, we found that the percentage of CD39 (OR; 1.028, CI; 1.006–1.052; p = 0.01), IL-10 levels (OR; 1.0, CI; 1.005–1.044; p = 0.02), and adenosine concentration (OR; 0.96, CI; 0.93 to 0.99; p = 0.007) were strongly related to severity. This evidence concerns the gene ENTPD1 and COVID-19.