Firefighters were not named in the original health order requiring vaccinations but were deemed to be covered by it because their work brought them into contact with medical personnel.
It applied to anyone who was within 2m of a medical worker for 15 minutes or more at a time.
The order will still apply to frontline health and pharmacy workers.
A Northland firefighter, who spoke on condition of anonymity, said although volunteers could return regardless of vaccine status from July 8, that didn't mean brigades would go back to being fully crewed straight away.
Some firefighters had been absent for more than seven months and would have to catch up on training before they were allowed back on the trucks. That could take two to three months, he said.
"It's not like we can flick a switch and bring them back right away because we can't."
While he understood the vaccine requirement early in the pandemic, some firefighters felt disillusioned by the way Fire and Emergency NZ (Fenz) had handled the issue and what they regarded as a lack of support from top levels of the organisation.
It was likely some wouldn't come back.
"A lot of people feel let down. It's really shaken them up."
With volunteers in short supply at the best of times, the firefighter shortage had been "extremely hard" on those who were left.
"It was months of stress and being under-staffed and not knowing when it would end. We were never given an end date, not even with the work done behind the scenes."
That behind-the-scenes work included a series of stories in the Advocate, parliamentary questions by National MP Shane Reti and lobbying by the United Fire Brigades Association.
The firefighter said it was fortunate the health order didn't last any longer. By August he believed even some of the biggest Mid North brigades wouldn't have been able to respond to daytime callouts.
Fenz Northland manager Wipari Henwood said he was looking forward to welcoming back firefighters who'd been unavailable due to the health order.
"It's good news for us and a step to going back to normality. That's what our people want," he said.
"We need every single member we have, especially in these trying times with Covid still in the community and flu and winter illnesses affecting our numbers."
Now the focus had to be on supporting the country's health workers, who were "doing it tough" and carrying a heavy burden on behalf of all New Zealanders, Henwood said.
In May a Fenz spokesman told the Advocate 26 Northland firefighters — one career firefighter and 25 volunteers — had either not declared their vaccination status, were partially vaccinated or overdue for a booster, and as a result had been stood down as required under the Covid-19 Health Order.
That amounted to 3.6 per cent of Northland's 731 firefighters, he said.
However, the actual number of firefighters affected was thought to be significantly higher.
An informal survey of 10 Mid North brigades found they had lost 32 volunteers between them even before the booster deadline. Northland has 40 fire brigades in total.
The brigade at Bay of Islands Airport, though not part of Fenz, is understood to have lost three of its six staff.
In response to a parliamentary question in May by MP Shane Reti, Internal Affairs Minister Jan Tinetti said 39 of New Zealand's 569 volunteer brigades had lost a quarter or more of their personnel as a result of the health order. The Northland brigades were Taupō Bay, Kerikeri, Whananaki, Rangiputa and Paparoa.
The current strike by Fenz staff applies only to paid personnel and is related to pay and conditions, not vaccine mandates.
