My wife is a retired research scientist who worked on influenza vaccines. Long before the covud madness she had told me how each years flu shot was formulated against the particular strains that were suspected of becoming the dominant ones in the coming season. Sometimes they guessed wrong and it was not very effective because a different strain would be dominant.
Yah, since all of the real vaccine development (not mRNA crappola) got offshored only 6 strains are “guessed”. If you miss the one that really comes to pass — everyone loses - except those that got paid in gov’mt $$.