[tzs]

> Incidentally, only half of people or less even in affluent countries get the annual flu shot. It is frequently believed to be relevant only for the elderly and at-risk demographics.

You are right as far as about half getting it, at least for the United States. Quite a few people who are not elderly or at risk get it. Here are the age breakdowns.

About 60% of the people under 18 get it [1]. Under 18 is about 25% of the population.

About 34% of 18-49 year olds get it. They make up about 42% of the population.

That makes under 18s who get flu vaccine about 15% of the population, and 18-49s who get flu vaccine about 14% of the population. If only 50% of the population get the flu vaccine, that would mean that 58% of the people getting flu vaccine are under 50.

[1] https://www.thenationshealth.org/content/47/9/E45