If the virus you're dealing with is so incompetent at spreading as those strains from early 2020 were that almost failed to reach R=1 despite being fully airbor

If the virus you're dealing with is so incompetent at spreading as those strains from early 2020 were that almost failed to reach R=1 despite being fully airborne (which we now know, but back then even experts fell for "airborne spread could not possibly be as slow as we observe!"), even something like 5% effective can be a swim or sink difference for the virus. That said, we are now in the omicron era and things are very different now (masks are a weak but nonetheless important tool for the project of "please take turns with sick leave, thank you very much", and nothing more, nothing less)