GSTM1 and anemia (phenotype): When the subgroup who had received blood transfusion were considered, the prevalence of moderate to severe anaemia (Hb<7 g/dL) at the end of the transmission season was slightly higher among children who had been transfused (5/43 (14.7%) in the placebo group compared to 2/30 (6.67%) in the SP group) but there was no evidence of interaction between intervention group and having been transfused (P = 0.350).