Frequency of MBL cases in COVID-19 patients vs the general population from the same geographic area studied before the SARS-CoV-2 pandemic. (A) Frequency of MBL among all COVID-19 patients, as well as (B) patients with moderate, severe, or very severe COVID-19, or (C) only very severe COVID-19, compared to healthy controls. (A-C) Further comparisons by sex and age groups. Gray bars represent the percentage of MBL cases in the general population, and dark bars represent the percentage of MBL cases among COVID-19 patients. Numbers over the bars are the percentage of MBL cases for each group. HC, healthy control.