Ardern said more nurses are required to give vaccinations in hard to reach communities.
"There is a need for a catch up campaign and we'll be rolling one out," she said.
New Zealand's Ministry of Foreign Affairs and Trade (Mfat) has said it is "highly likely" that travellers from Aotearoa were the main source for the Samoan outbreak, and Associate Health Minister Julie Anne Genter is now set to announce a major health campaign to close so-called immunity gaps within the New Zealand population.
A Herald investigation has obtained a Ministry of Health document from August last year, compiled by its communicable disease team with input from the national verification committee for measles and rubella elimination (NVC), a group of the country's top experts.
Measles outbreaks had hit New Zealand when the report was finalised in August, but hadn't yet taken off in the Pacific. Since May 2017 the expert committee made unsuccessful pleas for "catch-up" and targeted vaccination programmes.
"The NVC notes with disappointment that the recent increase in measles importation and subsequent outbreaks could have been avoided had its recommendations been acted upon in a timely manner," the ministry report stated.