What I'm saying is even if it was 100% infant mortality, the statistical odds of getting it still leaves the malarial resistance as a genetic advantage.
Sorry. I don't get your point.
Assuming 100% mortality, how could there possibly be an advantage if the genes of the afflicted cannot be propagated ?
Because not every person with the mutation gets sickle cell anemia. There is essentially a genetic burn rate that is less than the fitness imparted via malarial resistance.
People who have sickle cell anemia still have a life expectancy of years (>40 in US). On the other hand, getting malaria usually means you mortality is measured in days not years. Everyone has a "100% mortality" but the window of survival differs between diseases.