You seem to be having some difficulties here Jamie.
First, it is likely, as I explained, that measles was introduced to this vulnerable population from an infected person travelling from NZ, presumably Samoan islander, visiting their home country and family. But it is not certain - it would be very difficult to prove, but it had to come from somewhere and this seems the most likely route. There has been an epidemic of measles throughout New Zealand, but worst in south Auckland, the area lived in by many Pacific islanders who have been particularly vulnerable to the infection. .
Of the cases in NZ about half have been hospitalised. This is much more than the usual rate, which is about 10%. The reason isn't understood, but it's possible this particular "strain" of the measles virus is a bit more virulent. This might explain the large number of deaths in Samoa. No child has died in New Zealand but there have been two late miscarriages in women who developed measles in their pregnancies. Some children though have been very ill and required intensive care. There has been a significant shortage of MMR vaccine in NZ to try to stop this epidemic in its tracks and the government has been criticised for its slow and inadequate response.
The "poor public health" as a stated by me refers to two things, firstly the poor home and social conditions in Samoa, and secondly lack of good immunisation facilities and monitoring. This compares with other equally poor and socially deprived Pacific islands which haven't had measles epidemics and where immunisation rates are actually higher than New Zealand's. Proving to my mind at least it's not the poverty that causes measles epidemics but inadequate immunisation - what poverty and inadequate hygiene and living conditions is strongly associated with is the severity of the illness and the higher death rate.
Countries with MMR vaccination rates of over 95% include Mexico, Austria, Spain, Germany, Czech Republic, Latvia, Australia, Norway, Turkey, Denmark, Russia, Sweden, Switzerland, Belgium, Israel, Korea, China, Finland, Greece, Hungary, Japan, Luxembourg and Portugal. A varied collection of countries with very disparate populations and economies, going to show that achieving a 95% MMR immunisation rate is eminently achievable by any country.
It is true, sometimes immunisation will fail for whatever reason, but achieving a 95% immunity pretty well guarantees there'll be no epidemic spread of the disease to infect such children.
So I've answered every one of your questions, each of which appeared to be based on a position of ignorance - the mistaken assumption of the ineffectiveness or unnecessariness of the MMR vaccine. .