The generally pose the most danger to those either too young to be vaccinated, or who can't be vaccinated due to legitimate medical concerns. This is not uncommon, and such children rely on the herd immunity of their peers.

Further, as few vaccines are 100% effective, the herd immunity also limits the exposure of viruses to those for whom the vaccine was ineffective.

Makes sense, thanks.

Vaccination doesn't 100% guarantee immunity, so there is always a % that isn't immune. Each disease requires a different % immunity to prevent a wide-spread outbreak, i.e. to provide herd immunity. For particularly aggressive diseases it requires 95ish% immunity to avoid an outbreak.

So with anti-vaxxers increasing from roughly .5% to 1.5% over the last 10 years or so, that introduces a significant increase in the requirement of vaccination effectiveness, to the point where you wonder are we close to herd immunity breaking down.

In places with significant anti-vax sentiments, such as ultra-orthodox religious practices you will get those larger outbreaks of things like measles.

In general I think research indicates in the general populous anti-vaxxer populations are still small and disparate enough as to not impact herd immunity, but the trend has been upward due to the anti-vax trend over the last decade.

[source] am married to an M.D. that specialized in microbiology, recently listened to a good NPR bit about it that dropped the statistics, and I stayed at a holiday inn express last night.

The problem is some people with weak immune system cannot be vaccinated. So it's also for protection of these people.

They don't, un-vaccinated children pose a danger to children who can't be vaccinated for medical reasons.

It's herd immunity but it only works if the vaccination rate is sufficiently high.

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