A leading expert says there's no perfect way to roll out New Zealand's Covid-19 vaccine - and that "gaps will occur" whatever path is taken.
Rather, Immunisation Advisory Centre director Dr Nikki Turner argued, it was important the country's strategy stayed flexible, while ensuring it didn't prioritise the "worried well" over people with higher needs.
The Government's rollout aims to reach two million Kiwis within four months, with people at higher risk if they catch Covid-19 being the next in line behind border and healthcare workers.
Older people with relevant health conditions living in South Auckland, those in aged residential care homes or living in a whanau care setting will be offered the vaccine next.
Then from May Kiwis aged over 70, then those aged over 65 years old before the vaccine is offered to the remaining population in July.
The relevant health conditions to get early access to the vaccine include coronary heart disease, hypertension, stroke, diabetes, chronic obstructive pulmonary disease/chronic respiratory conditions, kidney disease, cancer and pregnant women.
While health experts have generally welcomed the Government's four-stage vaccination framework, some have suggested the plan could be improved by immunising all adults in South Auckland, or Kiwis setting off on short trips overseas.
Turner said that, ultimately, any decision the Government took would not "smoothly fit all needs".
"Essentially this is a mixture of protecting those at highest risk of contact with Covid, those at highest risk of severe disease if they did get Covid, and communities at highest risk of spread," she told the Herald.
"There are different priorities in all three areas here - and no single answer is ideal," she said.
"I think it is important to keep it simple as possible for all New Zealanders to understand, to focus on equity gaps and not leaving people behind, and... to be flexible and not rigid in decision making while having enough rules to prevent the traditional 'worried well' jumping ahead of those who have higher need."
So long as New Zealand could continue to keep the virus out, Turner said, there'd be time to roll out the vaccine in whatever sequence was chosen.
"We will have to shift rapidly, however, if we do see any significant community spread."
Otago University epidemiologist Professor Nick Wilson remained of the view that all adults in the Counties-Manukau DHB area should be in the second tranche of vaccinations, rather than just local people over 65 and those with high needs.
"This is because this population is particularly exposed to border failures via the proximity to Auckland International Airport and various MIQ facilities in South Auckland," he said.
"Nevertheless, it is to be hoped that such border failures will become less frequent with the vaccination of border workers – along with other refinements with MIQ to reduce mixing of people in shared exercise and smoking areas."
Dr Colin Tukuitonga, of the University of Auckland's Faculty of Medical and Health Sciences, was nonetheless pleased to see the South Auckland region prioritised.
"We've been lobbying for this to happen for some weeks now," he said.
"While we do this because we recognise the risk for the communities in South Auckland, they are also adjacent to the airport, so there is a risk of an outbreak to everyone else in the country too."
Thus, he said, prioritising South Auckland residents with these conditions and ages would be good for everyone, he said.
"The Government have decided not to vaccinate all of South Auckland as a priority, which I consider is a pragmatic response to limited vaccine supply," Tukuitonga said.
"There are other priority groups as well - the Government estimate 230,000 people live in high risk environments."
Like Wilson, fellow Otago University epidemiologist Professor Michael Baker thought the roll-out generally made sense, and the groupings weren't surprising.
But he offered some other candidates for earlier vaccinations.
"In keeping with the high priority attached to reducing the chance of future outbreaks it would be useful to consider vaccinating New Zealanders taking short to medium term trips overseas, such as those leaving with definite plans to return," Baker said.
"That would reduce the chance of them importing the virus when they come back. It might also be useful to consider vaccinating everyone on arrival in MIQ facilities, though that is a more complex decision as protection from the first vaccine dose would be only partial.
"It would of course be preferable to vaccinate all returnees prior to their departure to New Zealand, though that is harder to arrange at present."
Baker expected the current list of qualifying underlying health conditions would "almost certainly" be fine-tuned.
"One group to consider includes those who are obese, since we know that a high BMI is strongly associated with the risk of having a poor outcome from Covid-19 infection," he said.
"Children are still missing from the list for obvious reasons. We need data from trials that are underway at present to confirm that the vaccine is safe and effective in that age group."
Tukuitonga added it was a "fantastic decision" to allocate the 40,000 courses of the vaccine to Māori and Pacific providers to distribute to their patients and families.
"I know from experience that Pacific medical providers have predominantly Pacific patients, so it will improve the chances of the vaccine being delivered to those people that often have difficulty accessing health services."
Covid-19 modeller Professor Michael Plank, of Te Punaha Matatini, pointed out that Māori and Pacific people had a higher rate of needing hospital treatment for Covid-19 after controlling for age.
"It is a good start that the plan recognises this by prioritising older Māori and Pacific people," he said.
"It will be important that the Government continues to work with Māori and Pacific providers to ensure that there are sufficient doses available for these groups."
The priority groups
GROUP ONE: The 50,000 border and MIQ workers, their household contacts and the people they live with. This started last month and the vast bulk will be completed this month, with at least one dose administered.
GROUP TWO: Approximately 480,000 frontline workers and people living in high-risk settings. Starting with the 57,000 healthcare workers on community frontlines, and then moving through to healthcare workers protecting our most vulnerable and some priority populations. And anyone who lives in the Counties Manukau DHB area who is 65 and older or who has an underlying health condition is also in Group 2.
This started in February and will continue through to May.
GROUP THREE: Priority populations. Approximately 1.7 million people who are at higher risk if they catch Covid-19. This is planned to start in May.
GROUP FOUR: The remainder of the general population – approximately two million people. Starting from July.