Members of the administration have been echoing the herd immunity mantra of late, and Trump avoided answering a question about this last night. Maybe they have some inside information about vaccine problems they haven't told investors about yet.?.
ANYhoo, I think it appropriate to discuss what "herd immunity" for COVID-19 would really entail (in the absence of a vaccine).
First, I think it is appropriate to acknowledge that SARS-CoV-2, the virus, is endemic in the United States. It is too well established and too widespread to eradicate it easily. Second, it is reasonably estimated that about 10% of the population (33 million people, or about 4 times the confirmation rate) has already been infected conferring some immunity for an as-yet-unknown duration. Third, epidemiologists estimate that herd immunity would be obtained at a 65-85% infecting rate, given the virulence of the disease, and assuming no significant mutation. Those are my assumptions.
At present, we are at a plateau in infection and fatality rate: 50,000 +/- new infections and 750 fatalities/day. This has been true for over a month. Using these as estimates, recognizing that those numbers go up and down over time and are based upon treatment processes that currently exist, seems reasonable.
Given those bases, an additional 181,500,000 Americans would need to be infected to achieve herd immunity. At the present rate, that would take 2 years and result in an additional 564,000 deaths. That's on the conservative end.