Preparation is underway in case the Covid-19 vaccine arrives earlier than expected, Director-General of Health Dr Ashley Bloomfield says.
Meanwhile, Pfizer's New Zealand director will not confirm the number of doses to be delivered in the first quarter - but says the figures quoted by Bloomfield are correct.
Medsafe yesterday approved the Pfizer-BioNTech vaccine - which has already been given to millions around the world - for use here.
The first half million doses are expected to be delivered before the end of March.
Bloomfield told Morning Report today that Pfizer had been approached by New Zealand to see if the vaccine could be delivered faster.
"We're talking with them all the time about making sure they are on track with the timeframes and as you saw yesterday, they are on time with that."
Work to have the system - including storage - in place in the event the vaccine arrived early was underway, he said.
"All the different bits are coming together well and we have always said we are aiming for the first quarter and we have been redoubling our efforts over the past couple of weeks in case the vaccine comes sooner rather than later in this quarter, that we are ready to start vaccinating."
Pfizer New Zealand's Sydney-based medical director Krishan Thiru told Morning Report the company was on track and "doing everything we can to meet the conditions of our agreement with the New Zealand government".
That agreement is 1.5 million doses delivered in 2021 and the first batch by the end of the first quarter.
But he would not confirm the number of doses to be delivered in the first quarter.
"There are confidential provisions in the contract which I am not privy to speak to but I am aware what Dr Bloomfield said yesterday and we're absolutely committed to doing what we can to deliver on the doses and to support the New Zealand government.
"My level of responsibility within the company is not in terms of the contract so I have not seen the contract myself but what I am aware of is the figures that have been stated by the New Zealand government is absolutely something that we are committed to doing."
Thiru said Pfizer would be willing to discuss with New Zealand if more vaccines were needed - and if it could supply them.
"If there is a increased need from any country including New Zealand for further doses of the vaccine ... then we would be very willing to see if we can help out and assist with a greater supply."
But he could not guarantee an increased supply.
"I can't speculate - we're having discussions with 100 countries ... but what I do know is that we do have a greatly increased capacity to produce doses this year and we're very willing ... to have discussions with individual countries to find out what their needs are and fill those needs."
It was hard to know how long the vaccine would give protection for because it was "early days of this vaccine", Bloomfield said.
"Two things though - the Pfizer vaccine has been shown to be highly effective in clinical trials - over 90, around 95 percent effectiveness. That's effectiveness in any form of illness - not just in severe illness or preventing death, so that's symptomatic illness, so that's way higher than will most vaccines.
"The ongoing trials and the ongoing monitoring of people who have been vaccinated with give us an idea of how long the immunity might last but all the studies that are being done ... suggest that especially once people get that second dose they do have a good response and immunity does last for at least some months."
Thiru also said it was not yet known how long the Pfizer vaccine gave protection.
"The pivotal clinical trial that's being conducted ... continues for up to another two years. And that's in the 44,000 patients in the trial. We will continue to monitor those people over that period and we will continually provide that data to Medsafe.
"I think the data we have seen so far ... up to around six to seven months in so far has shown a maintenance of a very high level of immunity but it's yet to be seen how long that will last."
Pfizer had also tested its vaccine against new variants of the coronavirus.
"It is showing that particularly in the UK variant that level of neutralisation is maintained. A little bit lower in the South African variant but whether that has any reduction in ... real world effectiveness is yet to be seen.
"One of the great things about the technology that's being used in our vaccine ... is that if sometime in the future if there is a new variant that escapes the vaccine then we can easily modify the vaccine ... within 100 days and produce a new vaccine that covers those variants."
Vaccine doesn't give lifetime immunity
Some vaccines gave lifetime immunity with a single shot, while others required boosters, or others like the flu vaccine required yearly jabs to keep ahead of the virus changing, Bloomfield said.
"It's hard to know with this vaccine, but the reason you want immune response in the body (is because) the body has immune memory, it remembers and recognises that infectious agent when it comes along again and of course it will take long before we know just how long that memory lasts."
It was "absolutely important" people realised the vaccine did not mean people would be immune from Covid-19 for life.
The nature of the virus changing meant it was likely the vaccine would need regular boosters.
New Zealand had not considered giving people a single dose - rather than two - in a bid to get initial vaccines to cover more people.
That was because the outbreak here was not as bad as the United Kingdom - where that technique had been used.
It was also due to the fact that Medsafe had approved the vaccine as a two-dose treatment, three weeks apart, Bloomfield said.
One of the advantages of having four vaccines on order - as New Zealand did - and all at various stages of approval - was that different vaccines could be used in different age groups and different target groups, Bloomfield said.
He said the impact of vaccination on transmission rates overseas should become apparent quickly.
That was because of the number of doses being delivered in places like the UK and USA.
"I think the UK has now vaccinated 10 million people, so the impact on transmission, if there is an impact, should start to be apparent quite quickly and I think we're starting to see those emerging results ... we will be looking out for those."
Requirement for vaccination?
Those results reinforced the importance of getting border workers and their families vaccinated here in New Zealand.
"And it it reinforces the important of the vaccine for New Zealand's efforts against Covid-19 and getting really high coverage (of vaccinations) because this is going to be a really key tool in us getting ahead of this virus and opening the border and getting the economy going."
Work was underway to educate workers - for example those on the border - of the importance of the vaccine, Bloomfield said.
Making the vaccine a requirement was also being investigated.
"We are doing some work on that with the (workers') agencies and the workers themselves.
"Any legal ability would be on the employer. The government has made it really clear the vaccine will not be mandatory in New Zealand and I think that's the case in just about every country around the world.
"It's really about the employment relationship and whether there are legal or other ways (to get people to get the vaccine)."
Bloomfield said his focus was ensuring people had good information about the vaccine and the opportunity to be assured of it.