Here are some basics on herd immunity, and here is some more technical research if you’re interested in the details! 

Condensing all of our additional commentary!

From @palavra-valise

Herd immunity is even more important than that, actually. Those three people who are vaccinated when nobody else is could still get the disease (doesn’t necessarily work with protection against zombies themselves so I’m not going with the theme here) because with more unvaccinated people, there are more opportunities for bacteria or viruses to mutate, so the strain included in the vaccine would be too different from the circulating strain for it to offer much, if any, protection. That’s why each and every one of us has a responsibility to keep up our vaccines, for the good of EVERYONE in our society.

Basically, the unvaccinated people in the mostly vaccinated population are safer than the fully vaccinated people in the mostly unvaccinated population. That’s why, if anyone says “Why do you care? You/your kid are/is fully vaccinated,” you should punch that person in the face and then give them a 20-minute lecture about herd immunity and not being a self-absorbed twit and about our responsibility to society unless we choose to live on, idk, an island floating in space.

This is a really good point! 

I should also point out that vaccination is still important even for diseases that don’t show up in the human population a lot any more (or even just the local population), because often those diseases still exist in reservoir species that can transmit the disease, or in human reservoirs in other parts of the globe - which is how we’ve gotten the recent measles outbreaks in unvaccinated kids.

We should also point out (as other people have on this post - you guys are awesome!) that the vaccine-autism link has been repeatedly debunked by sound studiesand that the original paper it was based on has beendisavowed and was deeply scientifically and ethically unsound in the first place.

Also, @madeofpatterns brings up a good point - there’s variation in people’s responses to the flu vaccine in particular, according to the CDC, (just based on age, general health, etc, not the quality of the vaccine) which makes it even more important for a lot of people to get vaccinated, to build up that buffer to protect people who aren’t immune. 

Given that a lot of people are curious about vaccine safety and the vaccine testing process (and some of you have mentioned this - thanks to @randomguy319 !) we’ve got a bunch more information on the vaccine development process and their safety.

Here is a really good overview piece that explains the years of development that go in before a vaccine hits the market, and here and here are more from the CDC with lots of good links.

Both the CDC and the FDA have a TON of information on vaccine safety.

Bottom line: Every vaccine on the market or that will come onto the market goes through years and years of testing before even being tested in humans, and then goes through multiple rounds of testing in humans, before being approved by the FDA and continually checked for product quality and for any instance of side effects. Therefore, vaccines are really very safe. 

UPDATE: News from Disney reminds us how important vaccination and herd immunity are!