At the end of the malaria transmission season, the proportion of the children with anaemia (Hb <11 g/dl), was significantly higher in the control group compared to the intervention group (61.1% [875/1,433] versus 53.9% [766/1,422]) (PE = 12%; 95% CI 3%–20%) (p<0.001). Here, GSTM1 is linked to anemia (phenotype).