How Herd Immunity Works — And What Stands In Its Way

What will it take to finally halt the spread of the coronavirus in the U.S.? To answer that question we’ve created a simulation of a mock disease we’re calling SIMVID-19.

When you click “Run Simulation” above, you are witnessing how a disease can spread through a population and how increased levels of vaccination can stop it in its tracks.

We’re chosen to simulate a fake disease since there are too many unknowns to simulate the course of COVID-19. There are common features in how any infection spreads. When enough people are immune — through vaccination or natural immunity — a population achieves herd immunity. The disease stops spreading efficiently and starts to fade away.

How quickly a community gets to herd immunity depends on a number of factors. We’ve illustrated some major ones in the scenarios that follow.

What happens if a more infectious strain of SIMVID-19 predominates in a community? You can see in the simulation that even at a 75% vaccination rate, many people in our imaginary community of 400 will still get infected …read more»