There are two things that will eventually happen that happen sooner or later in every viral outbreak---though later rather than sooner in the US, thanks to Trump's incompetence.
One is that the population of those who are susceptible will slowly drop proportionately as survivors who have developed immunity are released from hospitals.
Two is that the proportion of those who are carrying antibodies will rise, and those can be transfused within blood plasma. The body replenishes those antibodies within 24 hours, so immune people can donate repeatedly.
I seem to remember that plasma has to be matched, the way transfused blood is, though the factors are not the same.
I'm wondering if such plasma transfusions could be used as a last-ditch measure to help people fight off the virus, particularly those whose immune systems are compromised.
If this is possible, that's a really good argument for flattening the curve, as the population might be able to collectively make its own vaccine. I hope trials are fast-tracked so we can see if this might work.