are only beginning to be incorporated (mainly overseas) as we have not set approved a serologic (blood) test to measure antibodies in those currently or formerly ANTIGEN positive (RT-PCR positive for virus nucleic acid). We know antibody is produced but the longevity and levels of protection are not clear.
That said, there is every reason to believe that immunity will be conferred and at least somewhat lasting. Other coronaviruses (e.g., SARS) and those of animals typically show a reasonable immunity following natural infection and those of dogs and cattle ( sufficient to produce vaccines.
A longer answer:
1) Always before we created a serologic (antibody test) and for viral infections could show 4x rise in antibodies (and early rise in IgM with later persistence of IgG). The focus on antigen testing now means we haven't had an antibody blood test. One such test was developed and starting to be in use overseas, but we really don’t have a handle on it.
2) Those case reports of pts. who recovered, tested neg on PCR, only to develop symptoms and test positive again later are most likely those who never cleared infection to begin with (lab error, immune system deficiencies, etc) but without antibody tests it was hard to say. Generally other Coronaviruses in humans and animals do produce extended immunity although their ability to mutate may have an impact on duration.
3) an overseas producer of a serologic antibody test is in heavily impacted Telluride, CO right now testing nearly the entire population and will repeat in two weeks. This will be the first and best community prevalence data. I only hope they will then pick some larger communities and hospitals to test alongside the antigen tests.
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