The Spanish Flu spread like wildfire -- made worse by a world war, at the time. Around 50 million died, including 675,000 in the US. That makes it about three times as deadly, in per capita terms, as COVID has been so far. And that's all the more remarkable when you consider just how much younger the country was at the time. Half of Americans were in their early 20's or before, back then, versus the median age being almost 40 now.
So, naturally, once that pandemic had burned through the vulnerable part of the population, it faded away, with the survivors having resistance that would make future similar strains less deadly. And COVID would do the same if we let it burn through the population. If we were content to lose another 1.4 million Americans to the disease, or so, it would then go away on its own.
Or we can, instead, use our brains and get it under control with vaccines and other counter-measures. And there's every reason to think that can work. Massachusetts, for example, has one of the nation's highest vaccination rates, and so, despite high population density and median age, it has managed to get this thing under control. In fact, it's been running negative excess mortality in 2021 -- in other words, fewer people have been dying than in a typical year. And the economy has gotten back to normal, with unemployment rates below 5%.