PBA – If enough people don’t vaccinate it affects the herd immunity. I explained this in detail in previous posts about outbreaks. In simple terms they don’t make the vaccines 100% effective because that would make them much more expensive. What they do is make them about 80 -90% effective (or less) and the rest of the percentage they rely on the herd immunity. So if s/o who isn’t vaccinated gets the disease, they can start an outbreak even amongst the vaccinated group. This has happened in a camp in the mountains recently a couple of years ago. A Frum Bocher went to England -over there he was exposed to either measles or mumps and came back to camp and started an epidemic. He came down with the disease even though he was vaccinated, but I think the person he contracted it from – wasn’t!
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