1) Here we have no deaths with age <40 years.
2) Only people that had no strong cross immunity develop enough antibodies to be seen in the standard test.
3) Do also not worry about news that tell antibodies do decline over time. This only indicates you have a good T-Cell immune response that will curb the production up again.
But one thing is clear. Antibodies act immediately and protect you with a high degree from all symptoms. T-cell need some time and after a high does might be a bit to slow.
4) This is exactly what we see here in central Europe. We overall are close to herd immunity but not due to antibodies. So we have heavily fluctuating infection numbers as e.g. 10 super spreaders are enough to raise the numbers by 50..100%. Or in France where groups drink together 500..1000%!
And as I already said about a month ago. Now dozens of expert believe that masks may help to produce immunity due to low aerosol doses.
Last: Do not believe any expert as in fact there are none: It's all (-most all) new knowledge and you have to gather enough information yourself. E.g. I just read - German doctors heavily prescribe HCQ!
I've labelled the Wyttenfacts 1) - 4).
A Wyttenfact is not always untrue - it is just pure speculation, or exaggeration, and therefore likely false.
1) Switzerland 6 deaths under 40 out of about 1800. Germany 37 out of approx 15,000 (sorry total figures approx).
Covid death is very age-related. But hits everyone.
2) No evidence at all for this that I have seen, but I'd be interested in what this is based on: links to papers please, not Wyttenfactoids. FWIW I would expect some level of cross immunity to exist, and that cross-immunity will confer some protection against infection enough to generate antibodies. Not 100% as Wyttenfact says.
3) There is no evidence that old people are protected 100%, or even 50% from COVID by having cross-immunity. We just don't know, All we do know is that cross-immunity prevalence will not be 1000X more for young than old, yet that is the death ratio, so clearly other factors matter.
4) No evidence here about close to herd immunity, not even more close than France. You need to start off with seropositive rates - which will correlate with overall exposure. No evidence that lack of superspreader events comes from greater immunity rather than better (Swiss) behaviour. Evidence please, not Wyttenfactoids.
Sorry I remain vague about whether a Wytenfactual assertion about "here" means Switzerland or Germany. Facts here for Switzerland:
Seropositivity in school children 2.8%
estimated 10% overall.
Children are more likely not to seroconvert (but not more likely to have cross-immunity).
It is possible that 10% seroprevalence equates in Switzerland to enough herd immunity to reduce transmission. We don't know, the detailed data makes this look unlikely: