That is how herd immunity works basically.
Whether we have enough immunity for that to happen.... fingers crossed.
But remember, we saw "77% decreases" in Spring 2020 too.
Certainly, the degree of our current decline is largely due to the vaccines.  But should not ignore the seasonality of this virus either.
The current decline is not solely due to the vaccines.
For example, in the Spring 2020: Between April 9, 2020 and June 3, 2020, New York had a 85% decline in cases!  Between April 9, 2020 and July 15, 2020:  New York had a 93% decline in cases!!
Point being, even without vaccines, we would be looking at big big declines right now. The declines are even bigger, because of the vaccines.
Whether we have vaccinated enough to truly eradicate the virus, we won't know until the fall.