What You Need To Know About “Herd Immunity” During Coronavirus

As the coronavirus pandemic continues, we continue to receive more information every day about how to contain it. We’ve learned the importance of social distancing and the health risks associated with having gatherings of people. We’ve been encouraged to #FlattenTheCurve — a major world-wide effort to stop the sharp upward trajectory of infection numbers by staying home as much as we can.

Now, you may be hearing another term being used when it comes to coronavirus containment and mitigating risk: herd immunity. Folks familiar with how vaccines work may already know this term, as herd immunity has an important function when it comes to generally preventing infectious outbreaks. But for the unfamiliar, “herd immunity” is what happens when enough people have been exposed to a virus — through transmission or vaccination — that they have built up resistance to it and it can no longer spread as easily throughout the population, which in turn protects people who have not been exposed or cannot be vaccinated.

“What stops a virus, what breaks the chain, is if enough people get infected and those people develop immunity,” Dr. Todd Ellerin, the chief of infectious disease at South Shore Health, in Massachusetts, told ABC News. “In fact, if enough people get infected, the virus can’t replicate in that host. If you have immunity, you can’t get infected because the antibodies swarm like an army.”

The theory behind herd immunity when it comes to coronavirus is that if enough people are exposed, eventually the spread will slow because they will have developed immunity to the virus once they recover. This immunity can be for life, like with the chickenpox. Before there was a chickenpox vaccine, people often sent their kids to play with kids who had it so they would get it, too. Expose them once, have them establish immunity, don’t worry about it again. But this won’t necessarily work with coronavirus. For one thing, COVID-19 is much more lethal than chickenpox. 

Not only that, very little is known yet about how coronavirus affects the immune system and whether people become immune once exposed. The virus could work more like the flu, which mutates every year, which is why you can get a new strain of it each flu season. There have also been reports of people testing positive for coronavirus after seemingly recovered, so it’s still unclear whether a person could be reinfected.

“It’s just too early for us to say,” Dr. Simone Wildes, an infectious disease specialist also from South Shore Health, told ABC News. “We think about when we get a cold, and then get another cold, it’s no big deal, but we don’t know with COVID-19.”