The Covid-19 Info thread (keep politics out please)

[Prediction? Pain.]

This guy says maybe at 20%

https://www.google.com/amp/s/amp.the...rticle/614035/

Interesting read. Thanks for the link.

But my takeaway is that nobody knows and that the popular notion of "natural herd immunity" seems to be missing the mark. A couple of the people quoted in that article who give numeric "herd immunity" estimates are mathematicians. One of those mathematicians (who studies chaos theory in Scotland) thinks it could be as low as 20%, but even then she admits that her calculations seem optimistic. Another mathematician, this time from Stockholm, thinks 20% is unlikely but that ~40% could be possible. The article next says that an epidemiologist at Harvard says that he thinks the range is anywhere from 20% to 60%, but that the lower end of that is more unlikely than the higher end. And finally, the article quotes a couple of other people -- biologists who study epidemiology and infectious disease modelling -- who cast doubt on the current lip service being played to "natural herd immunity" in popular discourse:

What's important to [one scientist], rather, is that people are not misled by the idea of herd immunity. In the context of vaccination, herd-immunity thresholds are relatively fixed and predictable. In the context of an ongoing pandemic, thinking of this threshold as some static concept can be dangerously misleading.

"During the last few months, we've started talking about 'natural herd immunity' and what would be used to block future waves," says Shweta Bansal, an associate professor [of biology] at Georgetown University who studies how social interactions influence infectious diseases. She worries that many people conflate academic projections about reaching herd immunity with a "let it run wild" fatalism. "My view is that trying to take that route would lead to mass death and devastation," she says.

Indeed, letting a new, rapidly spreading virus run unchecked in a population with zero immunity could mean that nearly everyone in a given location gets infected. With vaccination, the herd-immunity threshold is vital to guiding policy and medical practice: If about 90 percent of people are vaccinated against measles, for example, then, accounting for waning antibodies and variable immune responses, it's safe to assume that 60 or 70 percent are protected and the population isn't at risk of an outbreak. But that concept doesn't clearly apply when a highly contagious virus hits a population with zero immunity. Left totally unchecked, Bansal says, the percentage of infected people could go even higher than 70 percent.

By definition, dynamic systems don't deal in static numbers. Any such herd-immunity threshold is context-dependent and constantly shifting. It will change over time and space. It varies depending on the basic reproduction number -- the average number of new infections caused by an infected individual. During the early stage of an outbreak of a new virus (to which no one has immunity), that number will be higher. The number is skewed by super-spreading events, such as when one person in a choir infects 50 others. And the number in a dense city such as New York should be expected to be higher than that in rural Alaska. "Within certain populations that lack heterogeneity, like within a nursing home or school, you may even see the herd-immunity threshold be above 70 percent," Bansal says. If a population average led people in those settings to get complacent, there could be needless death.