Vaccines can prevent serious illness, disability and death, but their benefits depend on people actually receiving them. When vaccination rates fall, the usual question is how to support more people to get vaccinated. Yet that question may be too simple. A reminder, a conversation, a financial incentive or a more convenient clinic can all help, but they do not necessarily help everyone in the same way. That is the central insight emerging from a major analysis led by Dr Sarah Davies and Dr Clare French, both of the University of Bristol, and colleagues. To go beyond asking whether broad categories such as “education” or “improved access” work, the researchers took apart vaccine uptake interventions to examine their individual ingredients. It is a little like studying recipes: knowing that a cake tastes good is useful, but knowing which ingredients make the difference is far more helpful if you want to create a better cake.

What if depression is best understood as a process that gathers momentum, rather than a fixed illness that simply appears once enough symptoms have accumulated? A difficult week becomes persistent stress. Persistent stress demands more coping. Coping becomes exhausting. Sleep, appetite, activity and relationships begin to change. Those changes can then create fresh stress, pushing a person further down a self-reinforcing spiral.