The basic idea of herd immunity is simple — if enough people are immune to a disease, then even if a person comes into the community carrying the illness, they won’t spread it. The few people who aren’t immune are protected, because most of the people they interact with are immune and so they can’t get the disease.
This works really well if you have a vaccination for infections. Measles, for example, used to cause massive outbreaks and kill hundreds of thousands a year, but in most countries cannot spread further than a few kids these days. That’s herd immunity at work, and it’s a wonderful thing to see… More here.
Such a good article. So good.