Dear Bernard and all,
You said: "We should base our communication on research on people's health knowledge and not on what we think people know."
Yes indeed. We should resist the temptation to conclude that people have sufficient health knowledge [ https://www.hifa.org/dgroups-rss/who-bulletin-using-behavioural-science-... ].
Let's take the example of lung cancer, as November is Lung cancer awareness month.
We might assume that everyone knows that smoking causes lung cancer, but we would be wrong! I just did a quick google search and found that a whopping 60% of Chinese adults do not know that smoking can cause lung cancer and 96% were unaware that it can cause heart disease.
It is no coincidence that China has more than 300 million smokers accounting for 40% of the world's tobacco consumption... nor that there are more than 10,000 new cases of lung cancer diagnosed every day in China https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6312841/