Measles And Herd Immunity

Why the Texas outbreak is likely to grow.

Pictured: Influenza. Yes, I couldn’t find a stock image of the measles virus, but let’s be real only virologists and people who read the image captions will know that. Photo by CDC on Unsplash

Measles is in the news a lot at the moment, because for the first time in decades people are dying of the disease in the United States. There have now been three confirmed measles deaths in the U.S. — two children and one adult — which brings the running toll from the current measles outbreak equal to the total of the preceding 25 years.

And more deaths are likely to come.

Why do I say that? Well, it comes down to a concept that you’ve probably heard about during the pandemic — herd immunity. While the idea has been bandied about for years, it’s almost never explained properly. It’s also a vital part of how we prevent children from dying from nasty diseases.

Herd Immunity

One of the reasons that herd immunity is such a poorly-understood term is that it is fairly complex. There are three main ways that the term is used in the academic community:

1. The rate of individuals within a population who are immune to a disease.
2. The threshold of immune individuals within a population that it is necessary to reach to prevent cases from spreading. This is the context it was most widely used during COVID-19 — it’s the % of people who need to be immune from a disease to make epidemics…