• Incidence of first or only malaria episodes in each study cohort by 12 months of age.
  

• Incidence of first or only malaria episodes by group up to 12 months of age as per protocol analysis.
  
• Incidence of first or only malaria episodes by group up to 24 months of age.
  
• Incidence of multiple malaria episodes up to 12 months of age.
  
• Incidence of multiple malaria episodes up to 24 months of age.
  
• Incidence of overall and severe anaemia up to 12 months of age.
  
• Incidence of overall and severe anaemia up to 24 months of age.
  
• Proportion of humoral and cellular immune responses against malaria at 12 months of age.
  
• Total number of admissions and outpatient attendances up to 24 months of age.
  
• Prevalence of P falciparum parasitaemia and overall and severe anaemia at 12 months of age.
  
• Proportion of humoral responses and geometric mean antibody titres of polio, DTP and Hepatitis B at 5 months and of measles at 9 and 12 months
  
• Incidence of side effects in each group up to 12 months of age.
  

The study is a randomised, double blind, placebo-controlled trial of the antimalarial drug sulphadoxine-pyrimethamine administered intermittently at 3, 4 and 9 months of age through the EPI scheme at the time of routine immunisations.

Children will be randomized into placebo and SP treatment groups by block randomization, and it is expected a similar age distribution and a similar number of children in each group. Doses of sulphadoxine (25 mg/kg)-pyrimethamine (1.25 mg/kg) (SP) or placebo will be given by a health assistant according to bodyweight (a quarter of a tablet for those <5kg, a half for those 5-10 kg, and a whole tablet for children >10 kg). The tablets will be crashed and diluted with water for their administration.