Auckland has only half the number of Covid-19 vaccinators it needs for the rollout, the Counties Manukau DHB head says.
The city's district health boards said they needed hundreds more and they were frustrated at some stumbling blocks.
But some GPs said the DHBs needed to do more to get them involved.
There have been 62,000 doses of vaccine administered so far and another mass vaccination centre is due to open this week.
Counties Manukau DHB chief executive Margie Apa said as the effort ramped up they need more people.
"We have about 1200 vaccinators now trained in the northern region but we could easily do with twice that number of vaccinators ... that would be a big game changer for us," she said.
Auckland's three DHBs were working together to roll out the vaccine.
Their eventual target was 25,000 to 30,000 people a day, but that could not be done without more vaccinators, Apa said.
Lemalu Silao Vaisola-Sefo runs a Pacific-focused centre in Ōtara that has been running for less than a week.
They had been a short a couple of vaccinators every day, he said.
He was pleasantly surprised at the number of people turning up to get vaccinated, about 300 a day.
But that could be 1000 if they had more staff and the wait times would be shorter, he said.
Apa said there had been two stumbling blocks.
One was getting enough nurses and other vaccinators through the Pfizer vaccine training module run by the National Immunisation Advisory Centre.
The other had been waiting for the Ministry of Health to change regulations to allow those with no previous vaccination experience to be approved and trained to give the jab.
The ministry announced last week an exemption had been approved to train the "non-regulated" staff.
Ōtara vaccine centre head Vaisola-Sefo said getting those new, non-nurse vaccinators was key.
There was a nationwidenursing shortage already and his centre was getting by on borrowed workers.
"We've only just got enough to go round and the more sites we open ... our workforce becomes leaner," he said.
"Once we set another one up, for example, out West, and another one maybe in Counties, you're really going to stretch your resources."
Auckland doctor Api Talemaitoga said the DHBs needed to get more GPs involved.
While some big clinics were in the plan, he said those in small clinics were frustrated.
"There are a few of us who are just questioning each other, saying 'have you been approached? Have you been asked'," he said.
"We have enrolments of thousands of patients who know us, trust us. If there is any vaccine hesitancy they will discuss with us."
Patients asked him every day about when they could get the vaccine, he said.
Apa said getting small GP clinics involved was complicated because of the logistics of using a vaccine that expired after a few days out of the freezer.
But GPs insist that was easily managed.
Immunisation Advisory Centre national manager Loretta Roberts said it was not to blame for any hold-up on training, saying any requests the DHBs made for access to the online module were processed every day.
Roberts told First Up the centre had trained about 4500 vaccinators so far, there was no waiting list, and the programme would scale up further.
"As the rollout in the vaccination clinics increase both in number and size the DHBs will be planning and looking for more workforce and as that happens the training will open up to more people.
"There's lots of conversation at the moment on planning that next step and increasing the number of people going through the training."
The criteria for recruiting vaccinators to administer the Covid-19 jab has already been expanded to include physiotherapists, occupational therapists, dieticians, phlebotomists and speech therapists.
"The pool of vaccinators is continuing to grow," she said.
"We've got very great capacity for ramping up the numbers.
"The last few weeks we've had an additional probably 300 to 400 people going through per week."
Asked how long it would take to double the number of vaccinators, Roberts said that depended on the people being available for training - and the centre was "ready and waiting to go".