The disease will 'die out' (in quotes because it will not actually) if there are not enough targets that are susceptible to it. People infected by SARS-Cov2 se

The disease will 'die out' (in quotes because it will not actually) if there are not enough targets that are susceptible to it. People infected by SARS-Cov2 seem to infect two to six other people [0]. Reduce this number by 90% and we are well below one infection per infected, so it is not sustained. This assumes that everyone would be vaccinated. Currently we are doing something similar: each measure like wearing a mask, social distancing, meeting fewer people, ventilating rooms, finding infected people before they can infect someone else ("contact tracing") contributes to reducing the number of follow-up infections a bit. (This is why "but masks do not really work" is an ill-informed argument. They do not have to because they are meant to be used together with other measures to achieve reduction in spread) A vaccine will protect us passively instead of requiring us to actively following these measures and will therefore be a lot more convenient. [0] https://en.wikipedia.org/wiki/Basic_reproduction_number https://en.wikipedia.org/wiki/Basic_reproduction_number