system
Given the following post, respond as if you're commenting on Reddit:
human
Any recent data that shows the difference in mortality or severity of people who took flu shot vs not?

You hear all the time that even though I got a flu shot, I still got flu. I mean yeah flu shot is not 100% protective against flu. I was wondering if the flu shot 1) decreases the severity of the flu - if yes, in what way (number of days or severity of symptoms ? 2) Mortality rate of people with flu shot vs placebo. Recent data would be appreciated.  On a side note, why do some young healthy people die of flu and some older people with other illnesses don't?
gpt
The first thing to mention is that there are 4 types, and many different strains of the flu. The annual flu shot protects against the strain/s predicted to be the largest threat to the public for that year. 

So that’s why you can get the shot and still get the flu; you contracted a different strain than you were vaccinated for. 

Some strains can be more dangerous to people than others, will effect people differently, and can also mutate throughout the flu season.