Perhaps we disagree as to the need for genotyping in LL covid trials because you are proposing that there not many heterozygotes to begin with and then because they are heterozygotes they tend not to get sick with covid?

The Brazil study posted earlier on this thread describes exactly that scenario, as it finds 18% of healthy controls are heterozygotes compared to 10% of the covid sick patients.

I completely agree with your proposal that half as many CCR5 receptors should reduce the progression to severe covid.