Are You Sure You Understand Herd Immunity?

A closer look at what it really means and some common misconceptions

Craig Spencer MD MPH
Elemental

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Photo: Macau Photo Agency/Unsplash

The Covid-19 pandemic has made us familiar with terms more frequently used in infectious disease journals than in common parlance. But in conversations with patients, friends, and family, I’ve noticed that understanding of these terms is often inaccurate or incomplete. This is especially true when it comes to the concept of herd immunity.

Everyone seems to understand that herd immunity represents a crucial transition point for Covid-19, when the likelihood of getting infected drops and our ability to return to normal increases.

The questions around herd immunity have started to pick up as more Americans get vaccinated: How many more shots do we have to give before we achieve herd immunity? Are we already there? What about the idea that maybe herd immunity isn’t even achievable?

Before the headlines confuse your understanding of the term even more, let’s talk briefly about what herd immunity is and what people often misunderstand about it.

Defining herd immunity

For starters, let’s define it. Herd immunity (also known as community immunity) exists when a substantial proportion of the population is immune to an…

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