G6PD and Plasmodium vivax malaria: Six studies were clinical trials, two of which were phase 3, double-blind, double-dummy, randomised placebo-controlled trials in patients aged at least 16 years with Plasmodium vivax malaria and normal glucose-6-phosphate dehydrogenase (G6PD) enzyme activity who received chloroquine plus placebo, chloroquine plus single-dose tafenoquine, or chloroquine plus 14-day primaquine.