By comparison, a systematic review of 1,975 patients of all ages in endemic areas with vivax malaria treated with chloroquine reported a maximum fall in mean Hb from 12.2 g/dL [95% CI 11.9, 12.5] before treatment to 11.6 g/dL [11.4, 11.9] 2 days later, with recovery by day 42 (12.9 g/dL [12.6, 13.2]) [7]. This evidence concerns the gene GSTM1 and Plasmodium vivax malaria.