The purpose of this book is to better understand how to improve the health of individuals, populations and the global community. What are the major threats to health? What are the causes of poor health? What works to improve health? How do we know that it works? What are the barriers to implementation? What are the measures of success? These are some of the key questions that will be addressed in this book. The aim is to provide health practitioners and policy-makers with a broad overview of how to improve health and reduce health inequities, as well as the tools to make more evidence-informed decisions that will have a positive influence on health.

Indeed, countless decisions that affect health are made every day, whether at the level of individual health choices made by patients and the general public, population health policies and programmes made by politicians and public health officials, or global health strategies and recommendations made by an increasing number of players at the international level, including civil servants, non-governmental organisations (NGOs), philanthropists, academics, public–private partnerships and so forth. For instance, a mother takes time off from work to bring her child to the local clinic to be vaccinated. A student buys a fruit for an afternoon snack rather than potato chips. A 28-year-old woman who carries the BRCA gene for hereditary breast-ovarian cancer undergoes preventive surgery to remove her breasts and ovaries. A government passes a bill to extend parental leave to one year and to increase funding for early childhood development programmes. The World Health Organization (WHO) recommends increasing universal health coverage and social protection by strengthening primary health care as the foundation for all health systems. In each of the above examples, people were faced with a choice (i.e. to vaccinate or not, to eat a fruit or chips, to have preventive surgery or enhanced screening, to finance social programmes or reduce taxes, to promote vertical programming that focuses on preventing and treating a single disease or a more comprehensive approach based on primary health care), and a decision was made that will either improve or impair health outcomes.