Herd Immunity Simulator

written by Shane Killian
modified by Robert Webb
* - Vaccinated cell
* - Unvaccinated cell
* - Infected cell

Click on a cell below to infect it and watch how it spreads.

Immunization rate on left: Immunization rate on right: Same as left
Infection rate if not vaccinated: Infection rate if vaccinated:
Infection speed:
 
Results:
Total population: = vaccinated + unvaccinated.
Number infected: = vaccinated + unvaccinated.
% of population infected.
% of vaccinated population infected.
% of unvaccinated population infected.
% of infected that had been vaccinated.

Anti-vaccinationists point to examples of real outbreaks where more than half of those infected had been vaccinated. Surely if most of those infected had been vaccinated then the vaccine isn't much good, right? Wrong. The simulator above shows that this is exactly what we expect to find. This is because most of the community is vaccinated, so even though a much lower percentage of those vaccinated become infected, the total number may still be greater. It's a bit of statistical trickery on the anti-vaxxer's part.

See also my article about an anti-vax graph which made use of some other statistical trickery.