"recent studies show that flu vaccination reduces the risk of flu illness by between 40% and 60% among the overall population during seasons when most circulating flu viruses are well-matched to those used to make flu vaccines".From your own link:
However, it’s not a perfect science, and some years, the flu shot doesn’t match as well as we would hope. For example, in 2017, the flu strain mutated right in the middle of the season. As a result, millions of people got sick with the flu, and 80,000 Americans died, according to the CDC.
Get it yet. It only protects against the flu strain it is designed for.
Not
All
Strains