It seems to be the case that those who are vaccinated or have had covid (and therefore antibodies) are less likely to (a) become infected, (b) transmit the infection, and (c) suffer serious outcomes.
There still seems to be some debate as to the percentage reductions in (a), (b) and (c), but it is seems to be substantial. This is herd immunity in action, and the pool of people not yet protected in this way is getting smaller every day.
The reproduction rate of the original virus with no lockdown, masks, or distancing was ~2.5-3.0. The Kent (Alpha) variant was more transmissable, and the Indian (Delta) even more so. Therefore the "unabated" reproduction rate for Delta is (I assume) between 5.0 and 6.0.
The current reproduction rate is estimated at 1.0-1.3. As there are now fairly limited controls over interaction, I can only assume herd immunity is close to being an effective control.
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