Inhibition of IFN-mediated JAK/STAT signalling with ruxolitinib, evidenced by the absence of ISG induction (Extended Data Fig. 2e,f), rescued BA.1 and BA.2 infection in Calu-3 cells to a greater degree than BA.4 or BA.5 (Fig. 1g and Extended Data Fig. 2h–j), suggesting that the greater induction of IFNβ by BA.1 and BA.2 reduced their infectivity. Here, IFNB1 is linked to infection.