Samoa was warned repeatedly to improve measles vaccination rates, several months before the arrival of a deadly epidemic that has killed 77 people and sickened more than 5000.
The warnings undermine the government's argument it could not have prepared for the disease's arrival beyond its response, which included a mass vaccination campaign launched in November.
As early as March, the World Health Organisation and the UN children's agency UNICEF identified low vaccination rates - just 28 percent of Samoa's population had both doses of the measles vaccine last year - as a key risk amid a global resurgence of measles.
A letter issued to all Pacific Island governments at the time urged them "to take proactive measures to close immunity gaps and strengthen their systems to rapidly detect and respond to measles cases," a UNICEF spokesperson said.
The spokesperson said these messages were also delivered at an April meeting of Pacific health leaders in Fiji, and again at a Pacific Health Ministers meeting in French Polynesia.
Samoa's Director-General of health, Leausa Dr Take Naseri, attended both meetings according to publicly available records. Dr Naseri could not be reached for comment through a spokesperson.
At the April meeting, the threat posed to the Pacific by a measles outbreak in the Philippines - thought to have travelled to New Zealand and then on to Samoa - was raised directly by officials, according to Dr Siale Akauola, the chief executive of Tonga's Ministry of Health.
Samoa did not begin its mass vaccination campaign in earnest until 15 November, when a state of emergency was declared and schools were closed.
By then, seven people were suspected to have died, and hundreds more were sickened.
Samoa has since passed laws making measles' vaccinations mandatory, and briefly shuttered government this month to assist a door-to-door immunisation effort where unvaccinated people were encouraged to hang pieces of red cloth outside their homes.
The Health Ministry said on Thursday it had vaccinated 94 percent of the population.
However, dozens of fresh measles' cases are being declared each day.
Samoa's Prime Minister, Tuilaepa Sa'ilele Malielegaoi, has repeatedly defended his government's response to the epidemic.
When asked at a press conference last week if New Zealand could have done more to prevent the outbreak, he said "even Samoa couldn't do more".
Tuilaepa's claims are however at odds with many health experts, who say Samoa let its immunisation rates fall to dangerous levels.
"It's too late for those children who have died," said Michael Baker, a professor of public health at Otago University.
"Prevention is better than cure. I know it's an old cliche but it is true."
The opposition Samoa First Party, which has called for an inquiry into the measles epidemic, said the government's inaction over measles' vaccinations amounted to "gross negligence. "It's from one muckup to another muckup - this is a government of muckups," said its leader, Unasa Iuni Sapolu.