Herd Immunity

Today we’re going to talk about herd immunity. Despite what some folks on the internet may tell you, joining the herd does not make you a “sheeple”, it makes you socially responsible. You’ve no doubt heard the catch phrase “herd immunity”, recently changed to “community immunity” because it’s more fun to say and because the whole herd thing just makes it sound like you’re part of some mindless herd, blindly following the orders of your reptilian overlords. Nothing could be further from the truth. Herd immunity is not some made-up concept being sold to you by Big Pharma and the evil government. It is a well-established, thoroughly studied phenomenon and it’s very important. Not everyone can receive certain vaccines. Not everyone’s immune system responds to vaccines very well. Infants are too young to receive some vaccines. All of these people depend on the immunity of OTHER people to keep them safe from exposure. For most vaccines, we need a vaccine rate of about 95% to maintain community immunity (go ahead, say it out loud, it’s fun). When vaccine uptake rates fall below that, we start to see these diseases come back.


Another important concept to understand is that no vaccine is 100% effective. If I give 100 people an MMR vaccine, about 97 of them will develop immunity to measles. That’s pretty good (in fact it’s the best one we’ve got). The flu vaccine, on the other hand, will work for 40-60% of people. BUT, even vaccines that aren’t 100% effective can still erradicate diseases if everyone gets them because . . . you guessed it . . . herd immunity!




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