The discovery of insulin in 1921 changed the prognosis for people with type 1 diabetes. A century later, availability and affordability of insulin remain a challenge in many parts of the globe. Using the WHO’s framework on understanding the life cycle of medicines, this review details the global and national challenges that affect patients’ abilities to access and afford insulin. Current research and development in diabetes has seen some innovations, but none of these have truly been game-changing. Currently, three multinational companies control over 95% of global insulin supply. The inclusion of insulin on the WHO’s Prequalification Programme is an opportunity to facilitate entry of new companies into the market. Many governments lack policies on the selection, procurement, supply, pricing and reimbursement of insulin. Moreover, mark-ups in the supply chain also affect the final price to the consumer. Whilst expenses related to diabetes are mostly covered by insurance in high-income countries, many patients from low- and middle-income countries have to pay out of their own pockets. The organisation of diabetes management within the healthcare system also affects patient access to insulin. The challenges affecting access to insulin are complex and require a wide range of solutions. Given that 2021 marks the centenary of the discovery of insulin, there is need for global advocacy to ensure that the benefits of insulin and innovations in diabetes care reach all individuals living with diabetes. Graphical abstract

Background: Co-creation is the process of involving stakeholders in the development of interventions. Although co-creation is becoming more widespread, reports of the process and lessons learned are scarce. Objective: To describe the process and lessons learned from using the COHESION manual, a co-creation methodology to develop interventions aimed at the improvement of diagnosis and/or management of chronic diseases at the primary healthcare level in a low-resource setting in Peru. Methods: Observational study to describe the use of the COHESION manual 'Moving from Research to Interventions: The COHESION Model' developed for a multi-country project in low-and middle-income countries for co-creation and the adaptations needed to customize it to the local context of rural communities in northern Peru. Results: The actual process of co-creation in Peru included co-creation-related questions in the formative research; an initial consultation with stakeholders at the micro, meso, and macro levels (e.g. community members, health workers, and policy-makers); the analysis of the collected data; a second consultation with each stakeholder group; the prioritization of intervention options; and finally the design of a theory of change for all activities included in the complex intervention. The complex intervention included: 1) offer training in specific diseases and soft skills to health workers, 2) create radio programs that promote chronic disease prevention and management plus empower patients to ask questions during their visits to primary health care (PHC) facilities, and 3) provide a small grant to the PHC for infrastructure improvement. Small adaptations to the COHESION manual were necessary for this co-creation process. Conclusion: This study provides a practical example of the process of co-creating complex interventions to increase access and quality of health care in a low-resource setting. The process, components, challenges and opportunities identified could be useful for other researchers who want to co-create interventions with beneficiaries in similar settings.