It means that the longer it is has been since someone has been vaccinated the less effective it will be as the antibodies may dissipate over time. Example: Those vaccinated in December 2020 may be less protected than those vaccinated in May 2021.
But those months have to pass first...so this has not been going on “for months.”
But we still have the spike protein in our bodies - don’t we?
I’m more afraid of that than COVID.