Children who miss out on immunisation are more likely to miss out on all health interventions. Routine immunisation can strengthen the whole system, increase equitable access to many other health services and should be at the heart of a health system. Vaccination campaigns and the development of structures and strategies to reach every last child are often one of the baseline services, as well as a useful tool to strengthen, a primary healthcare system. In this short briefing, we highlight polio as an example to show the benefits immunisation campaigns can have on routine immunisation coverage and the wider health system.