We now know that the vaccines widely available (at least those used in the US, Israel, the UK) have waning effectiveness, likely requiring periodic boosters.
We also know those vaccines are non-sterilizing, meaning it is at least possible for fully vaccinated individuals to contract and transmit the virus.
Even assuming vaccine mandates in perpetuity, and widespread compliance, there will presumably be some overlap of "lapsed effectiveness" in the population between boosters. We literally don't have the capacity to administer boosters to all 200 million American adults exactly at the same instant, or even in the same month. Nor do we know for sure how long the effectiveness window lasts, or whether that may vary between individuals or type of vaccine.
How exactly are we going to "eliminate" covid, given this reality? Many Americans are terrified that the goal is "elimination" of the virus. Similar to the War on Terror, wherein we did a tremendous amount of collateral damage endlessly chasing an unattainable ideal.