Herd immunity is part natural (prior infection with SARS) and part acquired (vaccine/infection).
Please provide a source for that. First I’ve ever heard of that.
+++++
And as ‘herd’ immunity rises, so does the risk to those not protected - until the protection threshhold is reached.
And, a source for that ^, as it makes absolutely NO sense. As herd immunity rises....the risk for ALL DECREASES, from what I’ve always heard/read.
TIA.
definition of herd immunity: “resistance to the spread of an infectious disease within a population that is based on pre-existing immunity of a high proportion of individuals as a result of previous infection or vaccination.”
as stated, prior infection (sars is the prior covid infection) or vaccination.
Herd immunity is only reached when the threshold is met. If 80% herd immunity is required, 80% minimum have to have immunity; only 20% max can be unprotected. If 90%, only 10%. Increase the percent of unprotected and the percent herd immunity drops proportionately.