As I understand it, you want to screen out people with two copies of the allele (i.e. who are at risk for sickle cell disease) but not people who have one copy (i.e. people who aren’t at risk but still have resistance to malaria). So this doesn’t really seem like a problem to me? I.e. if you screen 100% of people, you can eradicate sickle cell disease, but people will still have and pass on the allele that gives malaria resistance.
As I understand it, you want to screen out people with two copies of the allele (i.e. who are at risk for sickle cell disease) but not people who have one copy (i.e. people who aren’t at risk but still have resistance to malaria). So this doesn’t really seem like a problem to me? I.e. if you screen 100% of people, you can eradicate sickle cell disease, but people will still have and pass on the allele that gives malaria resistance.