I readily admit that science doesn’t have firm answers yet for a LOT of questions about this relatively novel virus. And of course even the science can’t say anything for sure about a phenomenon that hasn’t yet happened. It can only make predictions based on past similar experience, which is exactly what informed people are doing in the case of “herd” immunity with this virus. And I note that your cited experts from J.H. didn’t have any quibble with the likelihood of herd immunity, just the cost in terms of morbidity, mortality and time required to achieve it
But we can be pretty sure from clinical observations and reporting so far that a large number of people fully recover and stop shedding live infectious virus after a variable period of time that usually does not exceed 2 weeks (it’s a gaussian curve and a noteworthy few are still shedding virus at a month). And this clinical recovery and eventual end to virus shedding is accompanied at about 2 wks post infection with a sharp rise in the Ig M (immunodeficiency-globulin M) curve. And at about the time that peaks the Ig G curve begins to rise and can rise for several weeks to a month…somewhat correlating with how long it takes to purge the virus. These are all observed facts AND are very much consistent with just about every other virus infection/recovery cycle that we’ve ever seen.
Now we don’t have enough data yet to say with absolute certainty that, in the majority of these cases, the patient’s Ig G is “neutralizing” and kills the virus in cell culture. But we do have some small number of good clinical observations that it kills the virus in OTHER PATIENTS, because the small pilot studies done so far on convalescent plasma treatment have mostly resulted in improvement. So based on all the fragmentary and incomplete data and past observations, it appears that very likely that infection with this virus DOES indeed cause immunity in the person infected. And immunity that can even be transferred acutely by means of convalescent plasma.
The other piece of evidence from past experience is that viruses that don’t confer good immunity on their hosts do not go away (eg: HIV, Hep C, Herpes simplex) in the absence of strong anti-viral therapy. So far there have been only a few anecdotal cases of people shedding virus for an extremely extended period or recurrently after testing negative. In none of those cases or small series that I’ve seen (and I’m following the JAMA & NEJM every few days) have any serous investigations yet been done to establish whether these were continuing or new virus infections (can be told from the virus RNA) or what the immune status of the patients was (immune deficiencies lead to weak or no immunity.
And of course there’s no evidence yet of this immunity that appears to be developing will be very durable. It MIGHT only last a period of months, which would not be good for herd immunity to develop. But the more common short end of the range of naturally acquired viral immunities is usually at least a year or so (and the long end of the rang is lifetime).
So, all in all, at this point it appears very likely that there will be SOME immunity out there in the “herd” of people who’ve had this infection and recovered (the VAST majority of those infected). But just how good, and how long we just won’t know for quite awhile.
Meanwhile, barring herd immunity, and barring artificial immunity conferred by vaccine (will be awhile) or immune globulin (probably not practical for the masses), this virus will continue to infect humans until either it reaches a level where potential remaining victims are just too sparse (“herd” immunity) OR the virus changes by means of genetic drift. The virologists are telling us that this virus appears relatively stable (compared to, say, “common cold” viruses and maybe even influenza viruses) so the first would appear more likely than the second.
As they say, “time will heal all wounds and answer all questions.” I’d say the two leading horses in this race are a successful, widely available vaccine racing against herd immunity.
PS: By the way, I saw Trump on TV strongly suggesting that “we’ll have a vaccine by the end of the year.” NOTHING YET published in the medical literature or even medical “news” via professional source would support THAT much optimism. I HOPE he’s right, both for our sake and his. Even though, if you listened carefully, he didn’t guarantee it, people will remember it and say “he promised us a vaccine by now” if we get to the end of the year without one.
PS: I went back and read this a couple of days later and I caught an unintentional error (reversal!) that probably doesn’t mean much to most people, but anyone up on their virus immunology would think I didn’t know what I was talking about if they read it. That is, I reversed Ig G & Ig M in talking about when the immune globulins produced by the body start to appear. “M” comes first and may be somewhat non-specific for the particular virus. “G” comes up later and is pretty virus specific and, hopefully, “neutralizing” which means is kills the virus (makes it unable to reproduce or spread). Sorry, I hope I didn’t confuse anyone or make anyone’s kid make an error on his hi-school biology report! I just reversed it due to a mental slip! I have made the correction above.