TNFSF13B and COVID-19: On the contrary, OPG and BAFF serum levels are higher in severe COVID‐19 compared to mild COVID‐19 cases (AUC 0.8, p = 0.0001; AUC 0.7, p = 0.0012; respectively) and moderate COVID‐19 cases (OPG p < 0.01), BAFF (p < 0.05).