Table 2.

Sample size for incidence

	Mali	Kenya	Zambia
Clusters per arm (overall)	38 (76)	35 (70)	35 (70)
Trial duration in calendar years (seasonality of FU) (total FU per participant time in months)	2 years (8-month seasons) (16 months FU)	2 years (12-month seasons) (24 months FU)	2 years (6-month seasons) (12 months FU)
α (type 1 error probability for 2-year trial)	0.05 (Haybittle-Peto with one interim analysis)	0.05 (Haybittle-Peto with two interim analyses at approx. 50% and 75%)	0.05 (Haybittle-Peto with one interim analysis)
Power	88%	80%	80%
Baseline incidence of clinical malaria in the target age group	0.40 events per person-year (based on 0.6 incident events during an 8-month malaria season) (5y– < 15y)	0.845 events per person-year during a 12-m malaria transmission season (1y– < 15y)	0.50 events per 6-month malaria season (Jan–Jun) (1y– < 15y)
Reduction in baseline incidence (incidence rate ratio = 0.70)	30%	30%	30%
Coefficient of variation	0.40	0.40	0.40
Assumed loss of person time, including true LTFU plus loss due to exclusion of person time following each treatment with AL	20%	20%	34%
Total person-years required (number enrolled per cluster before loss-to-follow-up)	3850 person-years (obtained by enrolling 38 individuals per cluster to account for loss-to-follow-up, followed for a total of 16 months)	1260 person-years (obtained by enrolling 13.5 individuals per cluster to account for loss-to-follow-up, followed for a total of 24 months)	1610 person-years (obtained by enrolling 35 individuals per cluster to account for loss-to-follow-up, followed for a total of 12 months)