The fallacy of herd immunity

TL;DR

This paper argues that herd immunity is not a controllable or reliable measure for epidemic control, and waiting for it is a misguided strategy, as it only signifies a paradoxical reduction in infection chances.

Contribution

It provides a novel interpretation of herd immunity, clarifying misconceptions and highlighting its unpredictability and paradoxical nature in epidemic dynamics.

Findings

Herd immunity cannot be reliably implemented or depended upon.

Waiting for herd immunity to halt epidemics is a flawed strategy.

Herd immunity is a reduction in infection probability, not protection.

Abstract

Here we show that herd immunity is not a measure we can implement, trust, control or depend on, and that waiting for herd immunity to play a role is tantamount to hope for the best. Herd immunity is not some protection, as it has been referred to, but a reduction in the chance of infection that a population can achieve only if more infections occur, which is paradoxical. The discussion on when there will be enough herd immunity for the COVID-19 epidemics to halt, delivers the public and policy makers the wrong message that we can wait for something to happen to relax containment measures. Here we review a non-orthodox construction of an epidemic that unveils what herd immunity really means, that is easy to understand by non-experts.