Implementing comprehensive, integrated, community-based health care for vulnerable communities in South Africa: An evidence-informed model In low and middle income countries across the world many poor communities have little access to health care. Providing health care is a challenge as the available national resources for health care is limited. People in these communities suffer from infectious diseases such as TB and HIV and from long term health conditions such as diabetes and high blood pressure. In poor communities many people with these conditions do not know they have them. Even if aware of their health condition, people may be unable to access the right treatment. Community Health Workers (CHWs) are local people trained to visit households in their community to identify people who are unwell, help them gain access to health care and support them in treatment. Existing CHW programmes have been successful in tackling infectious disease, as well as improving maternal and child health, but programmes usually focus on a limited range of health problems and do not cater for people with multiple problems. This project will design and evaluate a comprehensive integrated CHW programme that aims to identify and support the treatment of all types of ill health experienced in poor communities.  Research has demonstrated that CHW programmes are successful if there is good programme design, management, integration with the health system, and a good 'fit' with the community. However, there is insufficient evidence on how to operationalise these attributes for a successful comprehensive, integrated CHW service. Policy makers and service providers want to know how many CHWs are needed and at what cost, how are they best supervised, what is the best balance in terms of training, scope of work and household coverage, and how can they remain responsive to their community yet integrated with the health system? We aim to identify the key features of an evidence-informed CHW service model and the lessons for scale up.  South Africa is a middle income country with poor communities who have limited access to health care. The national Government is committed to strengthening primary care through the provision of community-based care by CHWs for these communities. The project will be undertaken in Sedibeng District, Gauteng Province of South Africa. Our collaborator, the District manager, is currently piloting three designs of comprehensive, integrated CHW programme, with different CHW-to-household ratios and different levels of access to supervision for the CHWs. Our objectives are to:  1) observe and interview existing CHW teams to understand how they work, and undertake a community survey to assess coverage, 2) using what we learn, in consultation with local, provincial and national stakeholders and international experts, to design an evidence informed CHW model then,  3) implement the model in two communities,  4) assess the impact by undertaking a survey of the community before and 15 months after implementation, as well as observation and interviews, and  5) to inform policy, implementation and practice.  The project results will inform the national roll out of these programmes by the South Africa Department of Health. By providing sufficient detail about the intervention, its context and evaluation, we expect governments internationally to be able to assess the applicability of the evidence-informed CHW model for their contexts and any adaptations needed. This will inform the use of resources for the provision of health care for poor communities, and the channeling of donor resources from high income country governments and other donor organisations, to maximise health benefit for poor communities. 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.