On 1 : I think that measles vaccines have to be 95%+ effective, or basically you have no herd immunity to prevent an outbreak and protect (for example) infants

On 1 : I think that measles vaccines have to be 95%+ effective, or basically you have no herd immunity to prevent an outbreak and protect (for example) infants not yet immunized. Because, measles is so amazingly transmissible. Other vaccines are much less effective (ie. yellow fever?) but because the diseases are harder to catch they can be suppressed in the population just as well.