Essential public health functions are not enough: fostering linkages between functions through National Public Health Institutes improves public health impact.

COVID-19 has highlighted the importance of essential public health functions (EPHFs) and the coordination between them. The US Centers for Disease Control and Prevention defines EPHFs as 'the public health activities that all communities should undertake'. According to multiple functional frameworks published in literature, the functions typically include workforce development, surveillance, public health research, laboratory services, health promotion, outbreak response and emergency management. National Public Health Institutes (NPHIs) are often the lead government agency responsible for execution of these functions.This paper describes how NPHIs or other health authorities can improve public health impact by enhancing the coordination of public health functions and public health actors through functional and organisational linkages. We define public health linkages as practical, replicable activities that facilitate collaboration between public health functions or organisations to improve public health. In this paper, we propose a novel typology to categorise important public health linkages and describe enablers of linkages identified through our research.Based on our research, investments in health systems should move beyond vertical approaches to developing public health capacity and place greater emphasis on strengthening the interactions between public health functions and institutions. Development of linkages and their enablers require a purposeful, proactive focus that establishes and strengthens linkages over time and cannot be developed during an outbreak or other public health emergency.