I became sick with the flu for the first time at age 16 and I am now turning 60. That was the sickest I've ever been in my life - high fever, delirious, etc. I never want to repeat that. I was so sick I truly thought I was going to die. There was no vaccine back then.
I usually get a flu shot every year, but kept putting it off this season(I was moving, remodeling, etc.) and caught the flu about the time I was finally going to go get the vaccination. Dang! I was pretty sick only the first 3 days (nothing like when I was 16 though, just sleepy, tired and puny).
I think my earlier flu vaccines actually helped me get through it without becoming any sicker than I was. My hub had only had a flu vaccine twice or so in previous years and he was a sicker longer than I was with this year. Generally, he recovers from most illnesses far faster than I do.
Stomach flu? Do your research. It is always water or food borne illness caused by ingestion of bacterial contamination or Norovirus. Either could be called "food poisoning", which is somewhat more accurate. Norovirus is completely unrelated to the actual flu but people persist in calling it "stomach flu".
After reading that, I'd be inclined to quickly leave any restaurant if someone threw up even far across the dining room.
There is no vaccine to prevent or treatment to cure Norovirus, but there are steps to prevent the actual flu in advance. One can prevent transfer of most any of the above by avoidance and proper disinfection.
I checked the CDC website when I had the flu. You are fully contagious one day before you experience even the slightest hint of symptoms, and remain contagious for five days after the first day you actually have symptoms. I delayed having Christmas with family until we had both passed those marks, especially since my husband's parents have become more frail and are both over 85. Neither has had a flu shot, by choice. If my father-in-law caught the flu, it would likely do him in.
One must be aware that the choice to not vaccinate oneself could mean one becomes a carrier a day or two before becoming ill oneself, exposing one's co-workers, one's own children, the children of others, and frail elderly people to the disease without even realizing it.
I fully believe that for the average person, the dangers of any vaccination are highly overblown and even if real for some folks, are far outweighed by the benefit to the vast majority. I am allergic and sensitive to a lot of things, but have never had a reaction to a vaccine of any kind, except perhaps a feeling of warmth in the body for a few seconds, or a slightly sore arm.
One must make their own decision, but should also realize that decision affects more than oneself. Whether one gets the vaccine or not, one should isolate oneself if one becomes ill. We had extended family drop groceries and at least one cooked meal on our doorstep while we were ill.