Quote Originally Posted by Mike T View Post
So a bit more than 10% have had it, if they are correct.
R varies with the organism, and with behaviour - in tight lockdowns it will be lower, with normal freedoms, higher.
And a low, or even zero R does not mean nobody is susceptible, it just means nobody is getting it, because of a
tight lockdown, for example.
The % of the population needed for herd immunity varies with R - and is 90% for an R of 10, 50% for an R of 2.
The results of more widespread serological testing will be interesting.
So let's say 10% have anti-bodies.

The school age population seems to have an immunity as well. That's 21%. (underlined by your Spanish study that showed presence of anti-bodies in children is nil - very low according to a Prof who's just discussed it on radio)

Then a proportion of the adult population have a natural immunity and defeat the virus without developing anti-bodies.

There's even a school of thought that smokers are less likely to catch (although if they do they are in more trouble) and they could be a barrier to cross infection. I can well understand this isn't put out there officially as the last thing the Govt wants is a spike in tobacco addiction.

It's quite easy to see how the traditional 60% herd levels thought to apply to such as flu may not be at play with CV, and note that SARS disappeared in the population.

And the cases of infection are dropping, especially when you consider that we have 10 times as many tests, and most of those tests are still mostly aimed at key workers assessed as higher risk, and suspected infected people the % of positives has dropped off a cliff.

It's lockdown perhaps? Or maybe it's pockets of herd immunity, or perhaps the overall levels of immunity/resistance are greater than many think.