Northland DHB has been pushing for a vaccination programme against a deadly strain of meningococcal disease for "some months", according to an internal memo from chief executive Nick Chamberlain.
But the Government only launched an urgent immunisation programme for Northland for the harmful MenW strain on Monday.
Three of the six nationwide MenW deaths were in Northland this year, where conditions for an outbreak were met on November 8.
The Government says it responded swiftly to the outbreak, but in a memo sent on Monday and obtained by the Herald, DHB chief executive Nick Chamberlain said the DHB had been pushing for a vaccination programme for "some months".
"We have been strongly encouraging the Ministry of Health for some months to approve this campaign as its the only truly preventative measure for our population," he said in the memo, which was sent to board members and the executive leadership team.
The Herald is seeking comment from Chamberlain.
Minsitry of Health deputy director of public health Niki Stefanogiannis did not comment on whether the DHB had previously requested a vaccination campaign, saying only that the ministry and the DHB had been discussing rising rates of meningococcal disease "for some months".
She said the ministry convened the Technical Advisory Group in late October that led to the urgent programme that was announced on Monday.
National's associate health spokesman Shane Reti said it appeared the DHB's efforts had fallen on deaf ears, potentially putting lives at risk.
"It's deeply disappointing. The DHB has been lobbying the Ministry of Health, as the document reads, for several months and getting no response until yesterday.
"The ministry has just taken too long to act."
Reti did not accept that the Government had acted swiftly.
"November 8 is the date when the outbreak criteria was met. But leading up to that were many indications of concern for a long time.
"It's only when it crossed that threshold for an outbreak that they started to do something."
The Monday memo follows a warning in May from Northland DHB microbiologist David Hammer about the rise in MenW cases.
In the May memo, Hammer encouraged colleagues to have their kids vaccinated, but this information was kept private.
Earlier this month, the DHB defended not telling the public following Hammer's memo, saying it did not want to alarm people unnecessarily, nor was it certain at the time if the cases were MenW.
Prime Minister Jacinda Ardern said she would ask questions about the May memo.
"On the face of that you would think that would be a trigger point at least for them to be talking to the Ministry of Health, absolutely," she told the AM Show.
The vaccination programme will start on December 5 in selected high schools and community centres across Northland. It will target people aged 9 months to 4 years (inclusive), and those aged 13 to 19 years (inclusive).
Pharmac has sourced 20,000 doses of vaccine that cover four types of meningococcal disease - A, C, W and Y.
One of those who died in Northland was 7-year-old Alexis Albert, whose mother Rowshae Albert also asked why the vaccination programme had taken so long.
Reacting to Alexis' death, prominent Northland GP Lance O'Sullivan vented his rage on Facebook, saying the issue had been handled poorly.
"I get f**ked off to see another brown kid in NZ dying from a f**ked up health system. Access to appropriate clinical care is the big issue. I am constantly reminded of how bad this sh*t is."
Director-General of Health Ashley Bloomfield has defended the response time, saying the outbreak was only confirmed on November 8, and it then took time to secure the doses - as both Australia and the US were dealing with outbreaks - and develop the programme.