community immunity as it is also known, is one of the main arguments that “pro-vaxxers” (those advocating vaccination) advance to persuade people to take vaccines. Herd immunity, so it is claimed, provides indirect protection to the unvaccinated. How? Here’s how the reasoning goes: if enough people get vaccinated, when a contagious disease hits a community, it spreads less quickly than if the majority were not vaccinated, since they are now protected. Thus, those unvaccinated few living among the vaccinated many can now enjoy some protection because the disease is finding it harder to spread and infect new individuals. This argument has many assumptions and flaws, as we shall see.