@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.
@VanGennepD @ADreyzen @FatEmperor 4/ Also clearly, no major change in public health measures have occured in this time frame, in fact things are looser than they were months ago. No new lockdowns, no masking mandates or fashions.
@VanGennepD @ADreyzen @FatEmperor 5/ Treatments and protection of the elderly have improved over the few months, reducing the IFR, but clearly those changes can only be minor factor when we see 100X reduction in mortality in the primary urban epidemic in Stockholm.
@VanGennepD @ADreyzen @FatEmperor 6/ The decline of the epidemic is completely compatible with the rising levels of immunity seen in Sweden, and follows a similar relationship to the epidemic collapses seen at similar seroprevalence in many locales, so there's nothing very mysterious about it.
@VanGennepD @ADreyzen @FatEmperor 7/ There may be a contribution from seasonality -- i.e, that the epidemic R increased and then fell due to vitamin D levels or other seasonally dependent factors. This is a kind of last-ditch-backed-in-the-corner argument for lockdownere, because if you believe that seasonality
@VanGennepD @ADreyzen @FatEmperor 8/ is the primary factor behind the up-down trajectories and the kinetics of the C19 epidemics across the world, then that completes undercuts any argument that lockdowns, mask, etc. are important. But, any port in a storm, eh?
@VanGennepD @ADreyzen @FatEmperor 9/ The Swedes have come up with three models or scenarios of how things will go over the next year or so, depending how much of a role seasonality is playing in the collapse of the C19 epidemic, which we just don't know.
@VanGennepD @ADreyzen @FatEmperor 10/ In one model there's another couple hundred deaths as this tails off this year and the immunity resulting is enough to keep this virus from seriously resurging next year. We end up with 6K deaths, full stop. At the other extreme, the immunity wears off and/or renewed seasonal
@VanGennepD @ADreyzen @FatEmperor 11/ effects such as reduced vitamin D from people staying indoors in the winter lead to a full resurgence and they go through the same cycle next year, albeit meliorated by improved treatments, etc.
@VanGennepD @ADreyzen @FatEmperor 12/ And the third scenario is that there is a significant seasonal effect & the virus does resurge next winter, but there's also significant immunity and the net effect is a more modest epidemic and some lower number of fatalities, further compounded by improved treatments, etc.
@VanGennepD @ADreyzen @FatEmperor 13/ Tegnell seems to favor a low-end intermediate scenario, which was countenanced from the start -- i.e., novel respiratory virus, initial high toll due to limited community immunity, then becomes endemic/seasonal, fading into the background of not-so-novel respiratory viruses.
