Uhhh well I presume health campaigns are things like cancer awareness things and the big stop smoking stuff?
So just write about them and why we have them (to raise awareness so that we can be more aware of what to do to prevent health problems)
They are usually effective because they scare you into being more healthy, e.g a stop smoking sign might have a picture of some mainly lungs on I?
And also people like the NHS will probably do these campaigns because it raises money to treat people, and using my smoking example, if less people smoke then it will be cheaper for the NHS as less people will have smoking related problems, just use lots of examples
I hope this helps