Are there any data available to support this claim? That would mean that the virus is cleared by the innate immune system and not the adaptive, but it is still a pretty bold statement.
The last I read (a Nature Genetics study, if I recall) was that the antibody quantity was lower in milder cases (but with a large inter-person variability).
> That would mean that the virus is cleared by the innate immune system and not the adaptive
Not necessarily, because adaptive antibodies produced through previous exposure to coronaviruses can also bind to covid19.
> Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective.
Very low levels, but still produced. (Note that I still have to dig through the paper.)
In addition:
> Plasmas collected an average of 39 days after the onset of symptoms had variable half-maximal neutralizing titers ranging from undetectable in 33% to below 1:1000 in 79%
Of course this is only a single study and more research is needed, but I notice people draw way too strong conclusions from studies that show low seropositivity prevalence.