A study in the Journal of Epidemiology was funded by four drug companies who sell flu shots: Sanofi Pasteur, Novartis, GlaxoSmithKline, and MedImmune. The study gave a number to treat for flu vaccinations in the elderly.
"The corresponding “number needed to treat” was 4,000; in other words, 1 death was prevented for every 4,000 elderly people vaccinated."
So those stats say that 3,999 out of those 4,000 elderly patients who got a flu shot would not have died anyway if they didn't get the vaccine. It doesn't help the 3,999; it only saved the one.
It's a gamble.