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The Nuance

Herd Immunity May Play a Bigger Role Than We Thought

Going forward, hard-hit communities could enjoy a measure of immunity-derived protection

Markham Heid
Published in
7 min readAug 27, 2020

During the first months of the pandemic, so-called herd immunity was a hot topic of conversation among public-health officials, politicians, and the media. The term refers to the percentage of people within a population that must have immunity to a virus in order to effectively retard or block its spread.

Early on, most experts estimated that the herd immunity threshold for SARS-CoV-2 was somewhere north of 60%, meaning that 60% or more of the population would need to develop immunity — either via vaccine or infection — in order to snuff out the virus. But those early estimates were based on incomplete data and overly simplistic statistical models — limitations that most infectious disease experts were quick to highlight at the time.

A lot of the data on the novel coronavirus remains incomplete. For example, researchers still don’t know just how infectious SARS-CoV-2 really is or how long immunity lasts following an infection. These two pieces of information are crucial inputs when it comes to accurately modeling herd immunity thresholds. Further complicating matters: The answers to both of these questions may vary depending on a person’s age, health status, and other factors.

But after months of real-world data, some recent research argues that the herd immunity threshold for SARS-CoV-2 may actually be lower, and maybe a lot lower, than initially suspected. Even if those estimates turn out to be overly sanguine, infectious disease experts say that some areas that experienced high rates of infection earlier this year could now enjoy some immunity-derived protection.

The latest herd immunity estimates and what they really mean

Recently, a team of researchers based in Sweden and the U.K. sought to produce a more accurate model of herd immunity. To do that, they considered the ways in which people of different age groups and social proclivities commingle in real-world settings.

The results of their model, which were published August 14 in the journal Science



Markham Heid

I’m a long-time contributor at TIME and other media orgs. I write mostly about health. I grew up in Michigan, but these days I live in southwest Germany.