TYK2 and infectious disease: Similarly, for the first time in critical care medicine or infectious diseases, a host genetic signal near the TYK2 gene30 led directly to the discovery of a new, effective treatment for Covid-19: baricitinib.31 This drug was one of 9 candidates under consideration for inclusion in the RECOVERY trial, and like others on the shortlist,32 had some support from bioinformatics predictions and small trials.33 The genetic signal influenced the prioritisation of baricitinib ahead of other potential treatments (personal communication, Patrick Chinnery, Chair, UK CTAP34).