The lowest percentage of patients with a Hb ≥2 g/dl drop was observed in Tororo in Uganda (Table 1, p = 0.015), which also showed the lowest mean age (26.6 months vs 33.8, 32.7 and 31.1 in Manhiça, Mbarara and Jinja, respectively, p = 0.0001) The Hb ≥2 g/dl drop was more frequent in children under 28 months (p = 0.026) with a high parasite density (p = 0.034), and without mild anaemia (p < 0.001). This evidence concerns the gene GSTM1 and anemia.