@VanGennepD@ADreyzen@FatEmperor 1/ Herd immunity in general just refers to the check on the spread of a contagion produced by rising immunity depleting available susceptible individuals.
@VanGennepD@ADreyzen@FatEmperor 2/ The herd immunity threshold is mathematically the percentage of the population which must be immune for an epidemic to go from the growth phase to recession.
@VanGennepD@ADreyzen@FatEmperor 3/ Clearly the epidemic in Sweden (and many other places) has been in recession for months, viewed at the national level. That doesn't mean that it's in recession everywhere in the country, just that net-net, declines outweigh new growth as the virus percolates into new regions.
@DocMcQuinn First, 20% by antibodies means 60%-100% actual infected & recovered, based on recent studies that looked at what fraction of recovered have detectable T-cell & mucosal Ab but not serum Ab responses -- a finding that's also consistent with several other observations and studies.
@DocMcQuinn NYC showed 20%-25% IgG+ in two randomized surveys conducted by the NYS Dept of Health as far back as late April, so presumably the great majority of NYC residents have been infected by now -- not surprising, given their high death toll & the total collapse of their death curve.
@DocMcQuinn Stockholm blood donors were 30% positive for COVID-19-specific T cells in May (about 3X the percentage of seropositives) and the Swedish FHM estimated a few days ago that the number of infected is now about 40%, which seems reasonable given another couple of months have passed.