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<p>As a matter of evolutionary biology, it is not in the best
survival interest of a virus to mutate to become more virulent. If
it does that, then it risks killing its host before that host can
achieve significant dispersal of virus particles. Consequently,
though there is a risk of virus mutation rendering vaccines less
effective, the tendency of mutation to create decreased virulence
will, to some extent, offset that effect. Of course, in the end,
this all comes down to numbers and the relative sizes of the two
effects.</p>
<p>Herd immunity is, however, not the only viable endgame. It is not
yet clear for how long any acquired immunity persists, nor what
factors affect the persistence time. In all epidemics there are
several factors that interact together to determine the course of
the disease in any given susceptible population. Further, <i>more
intense</i> second waves have been a feature of several
coronavirus epidemics and this possibility gives rise to all sorts
of uncertainty regarding the trajectory to the end of the
epidemic.<br>
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<p>Following the advice of my elder son, who is both a post-doctoral
bioscientist and a qualified civil engineer, I watched the Gresham
lectures on infectious diseases, epidemics, and Covid-19 given by
Prof. Chris Witty. These are easily found on the Gresham College
YouTube channel. I heartily recommend them to any non-specialist.
Also, at least so far, I've found the Covid-19 coverage in <i>New
Scientist</i> and <i>The Economist</i> to be far better than in
most other media titles.<br>
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<p>regards,<br>
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<p>Olwen</p>
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<p>PS: The term "pharma karma" has already been coined in advance of
Donald Trunt possibly developing a Covid-19 infection and kicking
the bucket as a result of hydroxychloroquine making it worse. ...
Far be it from me, however, to recommend the promulgation of this
usage. ... ;-O<br>
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<div class="moz-cite-prefix">On 07/05/2020 16:39, Derek M Jones
wrote:<br>
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<blockquote type="cite"
cite="mid:8e15214c-0faf-1c0c-dcfa-408a5169e835@knosof.co.uk">All,
<br>
<br>
One factor that is not getting much attention in vaccine
<br>
discussions is the risk that Coronavirus mutations will
<br>
significantly reduce the effectiveness of a vaccine; much like
<br>
what happens with flu vaccines:
<br>
<a class="moz-txt-link-freetext" href="https://blogs.sciencemag.org/pipeline/archives/2020/05/07/mutations-in-the-coronavirus-spike-protein">https://blogs.sciencemag.org/pipeline/archives/2020/05/07/mutations-in-the-coronavirus-spike-protein</a>
<br>
<br>
Herd immunity, or at least tolerance, does appear to be the only
viable end-game.
<br>
<br>
</blockquote>
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