Effects of a school-based water and hygiene intervention on the health and attendance of preschool pupils in Addis Ababa, Ethiopia: a cluster-randomised controlled trial

BACKGROUND: Children under the age of 5 bear the highest burden of disease related to inadequate water, sanitation and hygiene (WASH). However, evidence of the effectiveness of WASH interventions in preschool settings is limited. Nested within a cluster-randomised controlled trial in Addis Ababa, Ethiopia, this substudy evaluated the impact of a water and hygiene intervention on health and school attendance among preschool children. METHODS: Schools were randomly assigned 1:1 to receive the intervention during the 2021/2022 academic year or the following year (waitlist control). We included schools enrolled in the main trial with preschool classes and randomly selected and allocated additional schools with preschool classes to reach 20 schools in each arm. The intervention comprised school-wide infrastructure improvements (water storage and filtration systems, drinking water and handwashing stations) and hygiene behaviour change promotion. Planned sanitation improvements were not delivered within the trial duration. Within each school, we randomly selected 20 preschool pupils (ages 3-6), recording caregiver-reported diarrhoea, respiratory illness and absence over four consecutive weekly telephone interviews with caregivers of the selected pupils from April to June 2022, following intervention delivery. RESULTS: We found no evidence of effects on caregiver-reported diarrhoea (adjusted odds ratio (aOR) 0.85; 95% CI 0.46 to 1.59; p=0.61), respiratory illness (aOR 0.84; 95% CI 0.60 to 1.17; p=0.30) or absence (aOR 0.75; 95% CI 0.51 to 1.08; p=0.13). CONCLUSIONS: Dropout of three schools and challenges in telephone-based data collection resulted in large loss to follow-up, reducing statistical power. Further research should examine improving telephone-based methods to obtain sufficient follow-up data for school-based evaluations.