PROS1 and COVID-19: Recently, we demonstrated that a small proportion (<8%) of the general population elicited antibodies against MERS-CoV S protein, while most of sera from COVID-19 convalescent individuals (>60%) showed binding to MERS-CoV S protein, indicating that SARS-CoV-2 infection boosted antibody response with cross-reactivity against MERS-CoV (19).