Herd immunity kicks in somewhere less than 100% vaccinated (should start seeing some numbers coming out of Israel in the next few months). A sizeable percentage of the population has had Covid already and therefore has some level of natural immunity (not full, but better than nothing). Furthermore, kids have been shown to spread it less (and we're not vaccinating them currently, reducing the population 20-25%). So all that said, 100/100 is a pretty good short-term target. Yeah - we can and should do better in the long term, but ~100 should get us into a sustained decline (but not eradication - to your point about requiring more long term).