Oct 22, 2020 05:40 PM
https://www.nature.com/articles/d41586-020-02948-4
EXCERPTS: . . . Despite widespread critique, the idea keeps popping up among politicians and policymakers in numerous countries [...] Arguments in favour of allowing the virus to run its course largely unchecked share a misunderstanding about what herd immunity is, and how best to achieve it. Here, Nature answers five questions about the controversial idea.
What is herd immunity? Herd immunity happens when a virus can’t spread because it keeps encountering people who are protected against infection. Once a sufficient proportion of the population is no longer susceptible, any new outbreak peters out. “You don’t need everyone in the population to be immune - you just need enough people to be immune,” says Caroline Buckee, an epidemiologist at Harvard T.H. Chan School of Public Health in Boston, Massachusetts.
Typically, herd immunity is discussed as a desirable result of wide-scale vaccination programmes. High levels of vaccination-induced immunity in the population benefits those who can’t receive or sufficiently respond to a vaccine, such as people with compromised immune systems. Many medical professionals hate the term herd immunity, and prefer to call it “herd protection”, Buckee says. That’s because the phenomenon doesn’t actually confer immunity to the virus itself - it only reduces the risk that vulnerable people will come into contact with the pathogen.
But public-health experts don’t usually talk about herd immunity as a tool in the absence of vaccines. “I’m a bit puzzled that it’s now used to mean how many people need to get infected before this thing stops,” says Marcel Salathé, an epidemiologist at the Swiss Federal Institute of Technology in Lausanne.
How do you achieve it? Epidemiologists can estimate the proportion of a population that needs to be immune before herd immunity kicks in... [see article for the rest]
How high is the threshold for SARS-CoV-2? Reaching herd immunity depends in part on what’s happening in the population. Calculations of the threshold are very sensitive to the values of R, Kwok says... [see article for the rest]
Will herd immunity work? Many researchers say pursuing herd immunity is a bad idea. “Attempting to reach herd immunity via targeted infections is simply ludicrous,” Andersen says. “In the US, probably one to two million people would die.” [...see article for the rest...]
What else stands in the way of herd immunity? The concept of achieving herd immunity through community spread of a pathogen rests on the unproven assumption that people who survive an infection will become immune... (MORE - details)
EXCERPTS: . . . Despite widespread critique, the idea keeps popping up among politicians and policymakers in numerous countries [...] Arguments in favour of allowing the virus to run its course largely unchecked share a misunderstanding about what herd immunity is, and how best to achieve it. Here, Nature answers five questions about the controversial idea.
What is herd immunity? Herd immunity happens when a virus can’t spread because it keeps encountering people who are protected against infection. Once a sufficient proportion of the population is no longer susceptible, any new outbreak peters out. “You don’t need everyone in the population to be immune - you just need enough people to be immune,” says Caroline Buckee, an epidemiologist at Harvard T.H. Chan School of Public Health in Boston, Massachusetts.
Typically, herd immunity is discussed as a desirable result of wide-scale vaccination programmes. High levels of vaccination-induced immunity in the population benefits those who can’t receive or sufficiently respond to a vaccine, such as people with compromised immune systems. Many medical professionals hate the term herd immunity, and prefer to call it “herd protection”, Buckee says. That’s because the phenomenon doesn’t actually confer immunity to the virus itself - it only reduces the risk that vulnerable people will come into contact with the pathogen.
But public-health experts don’t usually talk about herd immunity as a tool in the absence of vaccines. “I’m a bit puzzled that it’s now used to mean how many people need to get infected before this thing stops,” says Marcel Salathé, an epidemiologist at the Swiss Federal Institute of Technology in Lausanne.
How do you achieve it? Epidemiologists can estimate the proportion of a population that needs to be immune before herd immunity kicks in... [see article for the rest]
How high is the threshold for SARS-CoV-2? Reaching herd immunity depends in part on what’s happening in the population. Calculations of the threshold are very sensitive to the values of R, Kwok says... [see article for the rest]
Will herd immunity work? Many researchers say pursuing herd immunity is a bad idea. “Attempting to reach herd immunity via targeted infections is simply ludicrous,” Andersen says. “In the US, probably one to two million people would die.” [...see article for the rest...]
What else stands in the way of herd immunity? The concept of achieving herd immunity through community spread of a pathogen rests on the unproven assumption that people who survive an infection will become immune... (MORE - details)