What is herd immunity?

Herd immunity, also called community immunity, population immunity, or mass immunity, has always been something of a buzzword since the beginning of the pandemic. It’s at the forefront of many popular arguments in favor of vaccination, to name one example, but are these claims valid?

What exactly is herd immunity? Definition aside, is it possible to achieve herd immunity naturally? If not, are vaccines the way?

What does herd immunity mean?

The definition of herd immunity, according to Wikipedia, is a societal state attained when the majority of the population is immune to a given pathogen, such as COVID-19. How?

Picture three types of people (we’ll continue using COVID for this example). You’ve got COVID-negative individuals with no immunity, COVID-negative people who are immune through one circumstance or another, and you have people who are already carrying the virus and are able to infect others in proximity.

Clearly, we’re not all just sitting around in a big room all day, but if we were, the carriers would start to infect those with no immunity. After getting sick and recovering, this second wave of cases would inevitably lead to some portion of those affected becoming immune in their own rights.

Once enough people in the room are immune to the virus and no longer able to stand in as a host, the virus eventually runs out of bodies to occupy. This is the big moment for herd immunity—with no way forward, the pathogen may be able to bide its time in victims where it has already established itself, but it won’t be able to continue to evolve unabated as it was able to previously.

What is the goal of herd immunity?

When all is said and done, we aspire to herd immunity mainly so fewer people end up getting sick. Any of the following may also occur as time goes on:

  • Rates of new infection may drop
  • Many people may now be immune to the pathogen
  • The pathogen may actually go extinct

It sounds awesome, right? We’re not quite there yet, though. What can be blamed for our lack of success against the coronavirus?

What makes COVID-19 a little trickier than the average virus: the fact that it mutates constantly because it’s transmitted so readily, outpacing COVID treatment and technology effective against its predecessors before it.

Mostly, public health experts hope to be able to make future COVID waves much more manageable than those in the past. The elimination of the virus entirely will always be something to strive for, of course, but moving toward herd immunity can still provide benefits to society in the short term—fewer deaths, fewer hospitalizations, and a public crisis that will be much easier to reckon with in the coming years.

Are COVID vaccines the answer?

If it were that easy, we wouldn’t need to get vaccinated for things like the measles and chickenpox; even though we do, plenty of people still get sick every year. Herd immunity is often a matter of chance—if the right people get together under the right circumstances, a new COVID outbreak may very well be possible, even with mandated vaccines.

In many ways, the COVID-19 policies that we’ve grown used to over the last two years sort of mimic the effect of an immune herd. Until we’re truly able to reach population immunity as an entire planet through cooperation and empathy for others, we may never get there.

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