Getting vaccine doses into the arms of 1800-odd unvaccinated border workers is a top priority and should be done as quickly as possible, a leading public health expert says.

But port bosses say the 11-week lead-in time for workers to get a single jab is necessary to limit workplace disruption, and even then exceptions may be needed to keep operations afloat if key workers - such as maritime pilots - still refuse to get vaccinated.

Yesterday Prime Minister Jacinda Ardern announced a change to the Public Health Response (Vaccinations) Order so it would apply to more border workers.

As of July 9, there are still 1766 border workers who are yet to have a single dose of the Pfizer vaccine - the majority of them port workers.

As of July 9, there were 1766 active border workers who were unvaccinated. (Photo / Supplied)

The expanded order will apply from Thursday, but the extra non-government border workers it captures - which make up most of the 1766 unvaccinated workers - won't need to get their first jab until September 30.

Government workers newly captured by the order will need their first jab by August 26. Any new border worker will need to have had one jab before they can start work.

It comes as the Government reopened quarantine-free flights to New Zealand from Queensland from 11.59pm last night, though anyone arriving without a negative pre-departure test will face a 14-day stay in MIQ - and a hefty bill.

Only about 50 per cent of travellers are being checked for a pre-departure test, and so far more than 50 travellers have been caught without one.

The pause on the transtasman bubble remains for New South Wales - which had 112 new cases yesterday.

New Zealand citizens and residents are able to return home on green flights with a 14-day stay in MIQ, though flights for the next two weeks sold out within minutes.

Ardern said the Government was still considering enforcement and privacy issues around making QR code scanning mandatory for bars and restaurants, and more widespread mask use at alert levels 2 and up.

She said it was an "extraordinary" step to make vaccinations mandatory for privately-employed border workers - even though she had said in April that all border workers will need to be vaccinated or they would be redeployed.

Otago University epidemiologist Professor Michael Baker said the unvaccinated worker gaps at the ports and airports should be plugged as quickly as possible.

"I'm sure there are logistical and other barriers to getting vaccinated, but we've got all of the infrastructure in place to administer the vaccine and track who needs it. The supplies are there. The staff to administer it are there."

The unvaccinated workforce at the border was the weakest part of our Covid defences, he said, following the decision to reduce the number of travellers from high-risk countries.

"If you look at what happened in Taiwan, Sydney and Singapore, those were all problems around workers connected with borders, but not MIQ workers."

Otago University epidemiologist Professor Michael Baker says unvaccinated border workers is currently the biggest weakness in New Zealand's Covid'19 response. (Photo / Supplied)

Ardern said the long lead-in time would limit disruption at the ports.

"There may be people in key roles that this will affect that will have a significant knock-on effect, if that particular worker chooses not to be vaccinated.

"We have allow the time for those workforces to readjust, if that is what is required."

Those key roles included maritime pilots, and specialised stevedore roles and crane operators, said Charles Finny, chair of the Port Company CEO Group, which represents 13 ports.

"It is very near impossible to recruit replacement staff in New Zealand in a hurry," Finny said.

"We don't want perverse outcomes here. We don't want the whole sector to shut down. We'll have to work through what mitigation needs to be employed for those people."

That could include allowing certain workers to work on the frontline while unvaccinated, or granting border exceptions to allow specialised foreign workers into the country who are willing to be vaccinated.

Finny said he did not oppose the expansion of the vaccination order "so long as we have the lead-in times, and so long as there is the potential for case-by-case exceptions".

He noted the port engineer who caught the virus last year had interacted with foreign maritime crew who had flown in to New Zealand.

"There's not been one incursion from maritime border yet. The existing policy has delivered extremely well, but this is a logical move and we were expecting it."

A vaccinations order came into force at the end of April, but it only applied to MIQ workers and non-MIQ Government workers at the border, such as Customs officers.

It did not apply to airside retail and hospitality workers at airports, or privately-employed baggage-handlers or airport cleaners - such as the one who caught Covid-19 in April after cleaning a plane that carried high-risk passengers.

It did not apply to non-government workers who come into contact with items that might be infected - such as the LSG SkyChefs worker who handled laundry from Auckland International Airport and who may have sparked the February cluster.

From Thursday, the order will be extended to cover the airside area of affected airports and some other higher-risk work at airports, affected ports, and accommodation services where specified aircrew members are self-isolating.

It will also include work that involves handling affected items removed from ships, aircraft, or MIQ, and workers who have contact with people who are subject to the public health order.

Covid-19 Response Minister Chris Hipkins said the lead-in times were a "maximum" and workers will be encouraged to get vaccinated as soon as they could.

"Of the active air border workers, 82 per cent are fully vaccinated and 2 per cent have received a single dose and await their second.

"However only 54 per cent of active port workers have been fully vaccinated, and we need to see this number increased to avoid the risk of Covid-19 entering the country via our ports."