Once again there is a study out showing people with blood type O ranking the best for overall protection while blood type A people rate the poorest.
Blood type O conveys protection against malaria because RIFIN, a protein secreted by parasites, bonds weakly with type O blood cells while strongly linking to type A.
Source: Goel S, Palmkvist M, Moll K, et al. RIFINs are Adhesins Implicated in Severe Plasmodium falciparum Malaria. Nature Medicine. 2015.
Once again the question pops up who mosquitoes are more likely to bite than others. Type O is the usual reply and though correct, more and more factors are being added at least as high possibilities in terms of significance.
Example:
Composition of Human Skin Microbiota Affects Attractiveness to Malaria Mosquitoes
Scientists have therefore been keen to learn more about how this species of parasite makes the infected red blood cells so sticky. It has long been known that people with blood type O are protected against severe malaria, while those with other types, such as A, often fall into a coma and die.