Contrary to the above, our result with serum ACE2 levels support a negative relationship between sACE2 levels and disease severity, as it is also apparent using rodent data on mACE2 in rat lungs, which yield a very strong negative correlation between estimated ACE2 levels and COVID-19 lethality across age and sex, in agreement with a mechanistic model of Covid-19 lethality (14). Here, ACE2 is linked to COVID-19.