The decision rule, however, is never the existence of a non-zero number. It is always a question of magnitude and whether that magnitude has meaningful impact.
Just to clarify this point: if you experiment with some simple SIR or SIRS models (which are not useful in modern epidemiology, but I digress) you will observe threshold phenomenon. This means that there will be broad ranges where perturbations of parameters (for instance, R0) have little meaningful effect on the progression of the outputs (for instance, the number of infected). Then there will be very small intervals where slight perturbations of parameters have a very meaningful effect on the outputs. For instance, there's not that much difference between R0=5 and R0=6, but there's quite a lot of difference between R0=0.999 and R0=1.001.
This is just to say that: it's plausible that vaccination has little to no impact on actual spread of Covid variants in the global population. I'm not saying this statement is true, I'm just saying that this statement is far from being disproven. There's just not enough evidence to call covid vaccination a "public good" and care about whether the low-risk get it.