Covid-19 Response Minister Chris Hipkins regrets the accidental release of data showing how much the country planned to pay for Covid-19 vaccines – and any impact the situation may have on New Zealand's "strong" relationship with Pfizer.

Yesterday, Newsroom revealed the Government expected to spend $36.50 per dose of vaccine from Pfizer.

The price of vaccines has long been kept secret by Government officials, citing commercial sensitivity.

The information was included in documents reportedly released by Hipkins in error in response to Newsroom's Official Information Act request regarding New Zealand's vaccine portfolio.

Hipkins told reporters at a press conference dedicated to boosters yesterday afternoon that the Government had a strong relationship with Pfizer throughout the vaccine rollout and intended to keep it that way.

"Obviously it was information that was not supposed to be released, so of course I regret that it has been released and certainly would regret any implication that that might have for the relationship with Pfizer."

The minister said his office hadn't had any discussions with Pfizer on the matter but the Ministry of Health, which handles the relationship with the pharmaceutical company, had.

When pressed further on the issue, Hipkins said he didn't want to get into the specifics of the information that was released as that would be "bad faith".

The documents obtained by Newsroom dated back to last March, April and May and indicated the 10 million doses of Pfizer vaccine purchased from the manufacturer would cost a total of $365 million - or $36.50 per dose.

For other vaccines, the Government reportedly agreed to pay $80.6m for AstraZeneca vaccines ($10.60 per dose) and $384.7m for Novavax jabs ($35.89 per dose).

According to Newsroom, it had also saved $85.5m for Janssen's one-shot vaccine, worth about $17.10 per shot.

At the same press conference, Prime Minister Jacinda Ardern announced the interval between the second Covid-19 vaccine dose and the booster would be reduced from four months to three months.

Ardern was joined by Hipkins, director general of health Dr Ashley Bloomfield and Ministry of Health chief science adviser Ian Town for the announcement.

The reduced interval meant one million more people in New Zealand would be able to get their booster from this Friday, when the change comes into effect for those aged 18 and over.

Ardern said it also meant 100,000 Māori and 52,000 Pacific people would be eligible for their booster from Friday, representing a 59 per cent and 47 per cent increase in Māori and Pacific people's eligibility respectively.

"I urge everyone eligible, go and get your booster as soon as possible," Ardern said.

"The reason is clear. Vaccination is one of the most important things we can do to prepare for and fight the current Omicron outbreak."

A big booster campaign would be run over February, and more details would be provided by the Ministry of Health.

On boosters for 12-17 year olds, Bloomfield said he was expecting advice from the Technical Advisory Group next week.

Yesterday, 38,332 booster doses were given meaning 69 per cent of those due for their booster dose had now received it.

Ninety four per cent of the eligible population had received two doses of Covid-19 vaccine.

The percentage of Māori who had received one dose of the vaccine was now 89.8 per cent.