I agree, but at the moment in China the only place that might have that level of immunity is Wuhan and Hubei unless one is going to assume that an extraordinarily large percent of the population when exposed shows no symptoms or does not require hospitalization. But, if this is the true situation then the numbers are all but meaningless since the true infection rate in Hubei will likely never be known.

But if the rate of infection needed to buy a level of immunity that renders the virus non-threatening (at least from a medical capacity/treatment point of view) is 20%, I do not believe that any country has reached that threshold and thus there remains the ongoing threat of future spikes in cases of the virus.