The roll-out of the Covid-19 vaccine for the wider New Zealand population has been moved back by weeks.

The Ministry of Health has changed the timeline on when the general public will be vaccinated from "from July" to "from the end of July".

In the latest update from the government this afternoon, Covid-19 Minister Chris Hipkins says he would not read too much into the wording change, and says the government was "endeavouring" to start vaccinating group four in July.

Hipkins says Pfizer has not given the government its delivery schedule for the vaccine from July onwards, but said it has committed to delivering all the vaccines by the end of September.

Hipkins says all DHBs have started rolling out the vaccine for Group 3 - over-65s, those with underlying health conditions - but the rollout is being affected by vaccine supply.

He says further vaccinations of the group will require more supply of the vaccines, which won't be until July.

"Everybody in that group will get more information, they don't need to do anything more until then."

Hipkins says the health authorities always envisioned there would be some overlap between groups, and that supply had always been a big factor on how fast the rollout could move.

"We're still endeavouring to start group 4 in July."

He says when Pfizer give a delivery schedule, they stick to it.

There have now been 562,149 doses of the vaccine given in New Zealand, with 85,000 receiving a vaccination in the past week.

Hipkins says 191,000 New Zealanders have received both doses.

With an expansion of saliva testing in frontline facilities, more than 1400 New Zealand border workers could look forward to less frequent invasive testing for Covid-19, Hipkins says.

He says saliva testing is an important step in mandatory testing and border workers would be able to choose more frequent saliva testing as opposed to their weekly nasal swab.

Some workers have had more than 100 nasal swabs.

"The ministry is satisfied that the combination of the two tests - the saliva test and nasal test - along with frontline border workers being nearly fully vaccinated ... will provide us with assurances that we need at the border to keep Covid-19 out of the community.

"Today's announcement means workers who have to be tested once a week because they are in important roles where the risk is a little higher, they can move to incorporate saliva testing to reduce the frequency of nasal swaps."

That would start from June, he says.

Recent Ministry of Health research showed the number of New Zealanders likely to get a Covid-19 vaccine is growing.

The survey done in April shows 77 per cent of people are likely to get the jab, up 8 percent from the March results.

-RNZ.