Background: In low- and middle-income countries, infectious diseases remain a key public health issue. Additionally, non-communicable diseases are a rapidly growing public health problem that impose a considerable burden on population health. One way of addressing this dual disease burden is to incorporate (lifestyle) health promotion measures within the education sector. In the planned study, we will (i) assess and compare physical activity, physical fitness, micronutrient status, body composition, infections with soil-transmitted helminths and Schistosoma mansoni, malaria, inflammatory and cardiovascular health risk markers, cognitive function, health-related quality of life, and sleep in schoolchildren in Côte d’Ivoire, South Africa and Tanzania; (ii) determine the bi- and multivariate associations between these variables; and (iii) examine the effects of a school-based health intervention that consists of physical activity, multi-micronutrient supplementation, or both.

Methods: The study is designed as a cluster randomised, double-blind, placebo-controlled trial with a 2x2 factorial design.  Data will be obtained at three time points; at baseline, 9 months and 21 months after baseline assessment. In each country, 1320 primary schoolchildren from grades 1-4 will be recruited. At each school, classes will be randomly assigned to one of four interventions: (i) physical activity; (ii) multi-micronutrient supplementation; (iii) physical activity plus multi-micronutrient supplementation; and (iv) no intervention serving as control. A placebo product will be given to all children who do not receive multi-micronutrient supplementation. After written informed consent by parents/guardians, children will be subjected to anthropometric, clinical, parasitological and physiological assessment. Additionally, fitness tests will be performed, and children will wear an accelerometer device for 7 days to objectively assess physical activity. Children infected with S. mansoni and soil-transmitted helminths will receive deworming drugs according to national policies. Health and nutrition education will be provided to the whole study population independently of study arm allocation.

Discussion: The planned project builds on the experience of a previous intervention study among South African primary schoolchildren. The present study involves three African countries with different social-ecological contexts, in order to investigate whether results are generalisable across the continent.

Trial registration: The study was registered on the 09 August 2018 with ISRCTN https://doi.org/10.1186/ISRCTN29534081