Allied, public health, scientific and technical healthcare workers have turned down the latest pay offer from district health boards.
More than 90 percent of the workers who were members of the Public Service Association (PSA) voted against it.
PSA Te Pūkenga Here Tikanga Mahi national secretary Kerry Davies said it was one of the strongest rejections of an employer offer that she had seen, a signal to DHBs their offer was "highly inadequate".
"For most of our members this offer is hardly a pay rise - in fact, when adjusted for inflation, for many of them it's a pay cut in real terms.
"This is not the way we should be thanking people who have been working on the front lines of our Covid-19 response, especially when they've been chronically underpaid for so long."
Davies said other healthcare workers in negotiations had received more substantial offers in the last year.
"We went into negotiations calling for the same treatment as our colleagues, but we've been refused", PSA member Janet Quigley said.
"It seems grossly unfair for our employer to treat one group of us so differently from others."
Covid-19 and staffing shortages meant it had been a tough couple of years for the health sector.
"New Zealanders can see the hard work we've been putting in throughout the pandemic - it's been really validating to know that they appreciate what we do.
"And our work isn't done yet. Our medlab scientists, for instance, will be busy all summer processing Covid tests to keep our communities safe as the borders reopen.
"We'll be going back into negotiations as soon as possible, and we'll keep pushing for a fairer deal - and we'll be considering all our options at that stage."
Allied, public health, scientific and technical healthcare workers deliver specialist healthcare services that sit outside the medical and nursing professions. They include pharmacists, medlab scientists, occupational therapists and physiotherapists.