A study with 88 patients infected with vivax malaria from Thailand identified that about 51.1% of these patients were intermediate metabolizers of CYP2D6 and had reduced enzymatic activity, thus putting them at risk of therapeutic failure and reinforcing the need to implement G6PD and CYP2D6 testing as an aid in the use of 8-aminoquinolines for the elimination of vivax malaria [15,35]. Here, CYP2D6 is linked to Plasmodium vivax malaria.