Furthermore, either type of IFN-λs, when used at a concentration of 100 ng (i.e., ∼3 and 2 IU of λ1 and λ2, respectively), but not at 10 ng, when combined with an otherwise ineffective dose of IFN-β (i.e., 0.05 ng/10 IU), could highly potentiate antiviral responses, resulting in the reduction of SARS-CoV replication by a factor of ∼50–75 at day 2 after infection (Figure 9). Here, IFNB1 is linked to infection.