ANALYSIS: A 'herd mentality' can’t stop the COVID-19 pandemic. Neither can a weak vaccine.

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ANALYSIS: A 'herd mentality' can’t stop the COVID-19 pandemic. Neither can a weak vaccine.

Fri, 2020-10-02 19:28 — mike kraft

A 'herd mentality' can’t stop the COVID-19 pandemic. Neither can a weak vaccine. These debates arise with every outbreak. Effective vaccination always wins. Science

Some prominent leaders wonder if herd immunity created as people are naturally infected with SARS-CoV-2 coronavirus would be enough to restore society to working order. For evidence, they point to hard-hit epicenters such as New York City, where approximately 20 percent of the residents have been infected and the caseload has been low and steady for months. This sustained recovery must be due to herd protection, they argue.

But based on simple math, past experiences with outbreaks, and emerging evidence from the ongoing pandemic, this claim is a fantasy.

“If we had reached sufficient herd immunity in New York, you would expect incidents to continue going down, not to be holding steady,” says Virginia Pitzer, an epidemiologist at the Yale School of Public Health who specializes in the mathematical modeling of how diseases spread.

A vaccine with 50-percent efficacy could spare hundreds of thousands from hospitalizations, chronic health issues, and death—but it couldn’t hit the herd immunity threshold on its own even if everyone took it. The safest bet is a vaccine above 75 percent efficacy.

A 237-page report from the National Academy of Medicine,https://www.nap.edu/catalog/25917/framework-for-equitable-allocation-of-covid-19-vaccine published October 2, lays out how to distribute such a vaccine in an equitable manner—while also showing how hard this process will be. A crucial step will be communicating how good the vaccine needs to be to stop transmission.

While major health agencies, including the U.S. Food and Drug Administration and the World Health Organization, say a COVID-19 vaccine should be at least 50-percent effective to be approved, this benchmark would actually be too low to establish protective herd immunity. ...

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