IFNB1 and COVID-19: On day 3 post infection, Delta P20 infection resulted in diminished IFN-β (p < 0.05) and IFN-ɣ (p < 0.05) production versus P0, which co-occurred with increased viral load (Fig. 3) and has been linked with more severe COVID-19 in humans (Fig. 6a, b)30,31.