[melling]

EFFICACY is a different word than effective.

https://www.cbsnews.com/newyork/news/sanofi-gsk-covid-vaccin...

“New vaccine demonstrates 100% efficacy against severe COVID, hospitalizations”

[ColanR]

The articles I linked used the two words interchangably. Clearly that distinction isn't relevant to the layperson audience. You're just playing with words.