You need to frame this in terms of quantifiable material loss to them in order for there to be a chance that they'd care.
So is your suggestion that medical policy based on balancing humours is actually effective altruism?
Our current policies favor fearmongering and cherry-picking to influence people to seek medical treatment that they don't need and come with side effects.
The fact that Doctors get paid a kickback for high child VAX percentages alone is enough to make me toss out the whole idea.