Previous research on the MERS-CoV and SARS-CoV S proteins facilitated by cryo-EM were instrumental in the discovery of the pre-fusion S protein stabilizing two proline (2P) mutations used in several vaccines that were rapidly developed to combat the COVID-19 pandemic (Kirchdoerfer et al., 2016; Pallesen et al., 2017; Walls et al., 2020). The gene discussed is PROS1; the disease is COVID-19.