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Sun 29 Mar 2020, 14:51 (last edited on Sun 29 Mar 2020, 18:01)
The great majority of people who recover from COVID-19 will have some immunity in at least the short term. If that wasn't the case, then people would me immediately prone to being infected again, and that clearly isn't happening; there are just a few isolated instances reported, and those aren't certain.
However, it's not clear how long such immunity will last. I was listening to a scientist who had been working on the persistence of immunity to the SARS virus, which is similar to the SARS-COV-2 virus which causes COVID-19, and they saw antibodies persisting for about 18 months, although with a reduced presence. However, he stated that the fact they couldn't detect the antibodies any more didn't mean that there was not some immunity or resistance still present.
There is also the issue of the virus mutating and evolving to bypass the bodies immune response. That's exactly what the 'flu virus does, and hence the wack-a-mole job of producing a new seasonal vaccine every year. At the moment, there is little evolutionary pressure for COVID-19 to be selected for such mutations as there are plenty of new naive hosts, but in time it's likely to happen (apparently there's not much sign of it yet).
It's also worth noting that there are several other corona virus strains which are endemic to the human population. Those cause about 25-20% of common cold infections every year.
Most likely the future of SARS-COV-2 is that it is endemic in the human population and will join those other corona viruses. Once this current wave is under control, then there is the possibility of another wave. That's what happened with the 1918 "Spanish" 'flu (a strain of the H1N1 virus), when there were three waves, with the middle one being the most deadly. However, nobody who recovered from the 1st wave was re-infected in the second.
In years to come, this will probably go from a virus that cripples economies and health systems to just another of the many respiratory viruses that plague and annoy people. However, it will probably never see a completely naive human population in that there will be some elements of resistance and immunity, so it will not spread so quickly and overwhelm medical systems.
I should also add that we've seen dress rehearsals with other zoonotic viruses with SARS and MERS, but fortunately neither had the characteristics required to evade containment measures.
On the subject of antibody tests, then they have to be reliable and not produce a lot of false negatives as that would mean a considerable number of people who could be still be infected at large in exposed roles. There have also been problems with some of the live virus tests being unreliable and with a lot of false negatives. The Spanish bought a large number of faulty ones from an (as it turned out) unapproved Chinese supplier and the Americans produced their own faulty tests which meant a large number of infections went undetected because of false negatives.
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