Interrupting transmission of soil-transmitted helminths: cluster randomised trial evaluating alternative treatment strategies in Kenya Some 1.45 billion people are estimated to be infected worldwide with intestinal worms, also known as soil-transmitted helminths (STH). Chronic and intense STH infections can contribute to malnutrition and iron-deficiency anaemia, and also can adversely affect physical and mental growth in childhood. Globally, STH result in 4.98 million years lived with disability each year. Fortunately, however, the global community is increasingly committed to tackling these infections, with many countries now successfully implementing geographically-targeted programmes that provide mass treatment to school-aged children delivered through schools. However, whilst school-based deworming has many important benefits for treated children, recent mathematical modelling suggests that treating only school-aged children will rarely stop transmission of these parasites, except in very low transmission settings, and that alternative approaches to treatment, including extending coverage and frequency of treatment, are required. To effectively deliver such expanded treatment, there is an associated need to evaluate the impact and cost-effectiveness of using community health workers to treat adult populations.   We plan to evaluate the impact of school- versus community-based treatment in reducing the transmission of STH species. A range of quantitative and qualitative assessments will evaluate the costs, cost-effectiveness, acceptability and feasibility of the different strategies and delivery systems. The study will be conducted in two contrasting settings in Kenya - south coastal and western regions - where an estimated 20% of the population are infected with STH. In order to maximize public health relevance, the study will be nested within the ongoing national school-based deworming programme, which is currently treating 4.6 million preschool and school children annually. The study drugs will be donated by GlaxoSmithKline and the full costs of delivery through schools and communities will be covered by the Children's Investment Fund Foundation, with additional input from the Government of Kenya. Cofunding for some of the trial activities are already funded by the Bill & Melinda Gates Foundation.   There is tremendous interest in conducting this study. The Government of Kenya, other national governments, funders and international policy makers are seeking clear policy and technical guidance as to the optimal approach to interrupt STH transmission. At the same time, countries are increasingly using community health workers (CHW; community members who provide basic health and medical care to their community, often on a volunteer basis) to deliver a wide range of health interventions, and there is a need to evaluate the benefits of using CHWs to deliver STH treatment. The proposed study, the first of its kind in Africa, will address these policy information gaps. Our proposed study is demand-led at the country level, with partners in Kenya supporting delivery and committed to scaling-up the new strategy, once demonstrated to be beneficial. Not only will the findings inform policy and practice in Kenya and other STH endemic countries, they may also lead to new WHO guidelines on the community control of STH and ultimately have demonstrable benefits for the impoverished communities affected by STH. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.