What!? This is an extraordinary claim that you state with zero evidence. It relies entirely on the naturalistic fallacy.
Not only is it possible for vaccines to confer better immunity but there are clear ways to test this empirically, which studies certainly have, like this one:
https://www.cdc.gov/media/releases/2021/s0806-vaccination-pr...
It looks at reinfection rates of unvaxxed people who had COVID vs vaccinated people.
