Doctors are being inundated with requests from over 65s who thought they could get their vaccine from this week - but can't.

The government's roll out plan says group 3 will be vaccinated "from May" - that is over 65s who do not fall into earlier groups, and people with conditions that make them more susceptible to Covid-19.

But the Ministry of Health says for most in the group of 1.7 million, the call-ups would not begin until the end of the month.

Auckland GP John Cameron said his surgery was flat out doing flu jabs and almost everyone was asking about Covid-19 too.

There was a lot of confusion, with many understandably assuming being eligible "from May" meant from the start of the month.

"From a punter's perspective, they want to know - am I going to get a vaccine, how am I going to be informed that I am going to get a vaccine - is it coming in the mail, is it coming from the DHB, is it coming from the ministry, is it coming from my general practitioner?" he said.

It was frustrating that most GPs knew little more than their patients did, he said.

His surgery was considering sending out an expensive all-patient text.

"Just to say, 'guys, we will let you know as soon as we know but we don't know at the moment'," he said.

Other GP surgeries from Auckland to Invercargill have told RNZ they have also been overwhelmed with requests.

Every DHB was doing things differently - with the ministry setting the overall strategy.

In Northland, for example, they were already rolling out to over 50s.

Gisborne-based Tairāwhiti DHB said it would do entire small, remote towns at once regardless of age.

Waitematā DHB chief executive Dale Bramley said Auckland's DHBs knew their populations best and would follow the government's guidance - with flexibility.

For example, if a whānau brought a kaumātua and kuia in to be vaccinated, and the younger members were ready too, they would try to do them at the same time, he said.

Dr Cameron said, to vaccinate as many people as possible, it was best to avoid missed opportunities.

If a nervous person or someone who did not visit often was in a surgery, that was often a great chance to give them their shot, he said.

"They don't have to come back, they don't have to rebook, they don't have to do anything else. It's done then and there," he said.

In a statement, the ministry's Covid-19 immunisation director, Jo Gibbs, said the rollout plan was a guide and she expected DHBs would have started to vaccinate those in the general over 65s group by late May.

Most people would receive an invitation but they would be staggered, she said.

Under the government's roll out plan, everyone under 65 not covered by other groups is likely to start getting their vaccine in July.