Prevention policy is quite efficient as far as it is not a care provider mechanism:tobacco smoking cessation
alcohol drinking should be limited to zero or a minimal amount per a day
exercise as frequently as possible
maintain a normal body weight through life
keeping a healthy eating pattern of whole foods
use drugs, hormones as less as possible
These decisions could be implemented in schools, universities, enterprises and communities. They are not relevant of insurance.
Illness is an event which is potentially treatable and relevant to insurance
Firstly illness needs a diagnosis
Secondly it needs a treatment whose benefit does not outweighs the risks
Screening is a research of illness and should obey to the same ratio of benefit/risk.