First, we were unable to 1) concurrently enroll a critically ill age-matched non–COVID-19 control group at our ICU to define the peripheral mucin mRNA signature in this patient group and to 2) collect mucus samples from non–COVID-19 ICU patients receiving invasive ventilation to calculate which mucins were differentially expressed in the lungs specifically due to COVID-19. The gene discussed is MUC5AC; the disease is COVID-19.