“With a disease like this, you probably need somewhere on the order of 60% or more people to have immunity in order to prevent an epidemic. Right now, if we’re at less than 5%; you would need at least ten- to twelve-fold that level. The only way to get there is to vaccinate people or else have horrific transmissions, and we can’t do the latter. So we’re going to have to continue some social distancing efforts.”
Medicynical note: There doesn’t appear to be a large number of asymptomatic people testing positive. That means, if true, that we’ll need a vaccine to safely reach the point where herd immunity offers protection. Not good news as a safe effective vaccine may be very difficult to develop. The covid-19 infection is unlikely to go away like “magic”—we tried that strategy already.