CHMP5 and COVID-19: Prefusion stabilization through the insertion of two proline mutations was shown to be successful in preventing postfusion transition in the SARS-CoV and MERS-CoV Spike proteins (22), and a similar SARS-CoV-2 Spike design serves as the antigen for the recent COVID-19 vaccines (which have shown up to 95% efficacy in clinical trials) (38, 39).