
Covid-19: Not all patients develop protective antibodies - polskibus
https://medicalxpress.com/news/2020-08-covid-patients-antibodies.html
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lbeltrame
This doesn't mean there is no immunity.

First of all, from the paper itself:

> Since we could not perform additional virus-neutralization tests we cannot
> exclude the possibility that COVID-19 convalescent subjects produce other
> types of protective antibodies besides those inhibiting RBD-ACE2 binding.

Second: they took antibodies from serum, which would exclude mucosal responses
(IgA), observed by other groups.

Third: There's the whole matter of T-cell immunity which is not touched by
this paper at all.

The antibody-dependent enhancement test was done in vitro, so there is no
guarantee it would happen in vivo. In fact, the authors say so themselves:

> However, studies are needed to investigate if antibody-mediated increases of
> RBD binding to ACE2 have a clinical relevance.

I'd add that a few vaccines in trial use the full-length spike protein, rather
than just the so-called "receptor binding domain" (RBD; the part that binds to
the ACE2 receptor), so more data are needed to see what is observed here has
implications or not.

Personally, I'm still optimistic.

