>2. (This is more to the point Gupta was making, which is in the context of 55,000 new infections daily in the US, with multiple vaccine strains out there) Supposing that the vaccinated person is exposed to virus strains for which the vaccine is less effective. The virus would be able to replicate (and thus have the chance to mutate, as well) more effectively than a common strain for which protection is provided by the vaccine.

Fauci and others have stated openly that the vaccines (when taken in full based on the recommended guidelines) provide very strong protection against mutations (Fauci made the point less than a week ago about the additional protections offered by the 2nd vaccine)

I'm sorry to say this, but I really think you're confusing this with people who start taking antibiotics but don't finish the prescription.
Sorin, you really need to go back and re-read what you're saying.