[rst]

This also assumes that acquired immunity from an infection is complete and permanent. Immunity to other coronaviruses decays over a year or two -- meaning that before the five years are up in your scenario, there would be a significant cohort of prior victims open to reinfection.

See, e.g., https://www.nature.com/articles/s41591-020-1083-1

[sfblah]

So, maybe that means by slowing the infection, what we're really doing is ensuring a neverending slow wave of infections ... forever? Maybe what normally happens with these kinds of viruses is they infect everyone then die out? And if you slow that, they never die out?

[emodendroket]

I don't think so. For instance, coronaviruses are among the causes of common cold. That one seems to have been with us for a while.

[D_Alex]

OTOH, a large number of infected people means a large pool of viruses to mutate into potentially re-infective strains.

[rst]

No, it means that the expectation that "herd immunity" will be naturally reached, without an effective vaccine, is a pipe dream. Before vaccines, no population ever reached "natural herd immunity" for polio, which has similar R values; you need effective vaccines, effectively delivered, to get that result.