There is a "lack of urgency" around vaccinations, in particular the bivalent Covid-19 booster, the Immunisation Advisory Centre says.
The updated Omicron-targeted vaccine (Pfizer BA.4/5 bivalent vaccine) has been available for those over 30 since the start of April.
Ministry of Health data, last updated on 12 May, showed 893,157, or 52.5 percent, of those eligible have had a second booster, and 289,402 had received a third booster dose.
Immunisation Advisory Centre medical director Nikki Turner told Checkpoint the uptake on Covid boosters was concerning.
"Now we have got the fourth wave of Covid now, it hasn't yet fallen into a winter pattern, but it is still with us and we don't know when the next wave will be," Turner said.
"I think eventually we'll expect it to fall into a seasonal pattern. But at this stage, it just keeps coming in waves," she said.
"So we need to continue to think Covid is there. It is real. It is still killing hundreds and hundreds of New Zealanders every year and we'll continue to do so."
"It's targeting those who are at higher risk" - Immunisation Advisory Centre medical director Nikki Turner
People were becoming complacent, Turner said.
"There is a lack of urgency. I think we've had this problem always with vaccines. It's out of sight, out of mind," she said.
"People forget until we see and feel the disease, how bad it is. We've come through a really bad pandemic, but now we still have a bad disease with us.
"So we have lost the urgency to worry about the disease. Same for flu. Flu is a killer as well. And yet we are too complacent. We take it for granted until it really affects us."
There were probably a range of reasons why uptake had been slow, including fatigue from the pandemic, Turner said.
"I think people are just feeling we've been there, done that and we've moved on, you know, it's a bit like flu, you forget what an important disease it still is in our community," Turner said.
"But there's a whole lot of other reasons as well. I think we've got a bit of a polarised community. There's a lot of anti-vaccination [beliefs] in the media, in social media. Some people feel very damaged by living through that mandate period in our history," she said.
"And there's some systems issues about just getting out and making sure you can get a vaccine."
Immunisation Advisory Centre medical director Nikki Turner Photo: RNZ / Angus Dreaver
There was also still a bit of confusion about the purpose of this bivalent booster dose, Turner said.
"A lot of people are at [still] risk of Covid disease, particularly older people," she said.
"Older people are 40 times more likely to end up in hospital than younger people, much more likely to die.
"Unvaccinated people are much more likely to end up in hospital, [and] people with medical conditions, so even if you've had Covid, even if you've had three vaccines to date, you're still at risk of Covid for many people, but not so much for everybody now, it's targeting those who are at higher risk."
Ministry of Health data showed 35.3 percent of those in the 50 to 64 age group and 69.1 percent of those aged 65 and over have had a second booster.
Boosters also helped to pick up waning immunity, Turner said.
"Vaccine immunity works in a similar way [to infection immunity] to protect us. But it does wane and you need boosters think again, similar to flu vaccines, we need boosters to keep our immunity up.
"I think what many people don't recognise too is that younger people get a better, stronger immune response as we get a bit older, we're more likely to suffer more severe consequences of Covid."
The bivalent booster is available to all adults from the age of 30 and over, as well as people with serious medical conditions and pregnant women.
"If you've got bad asthma, if you've got heart or lung or kidney problems, the vaccine really really helps protect you against bad Covid," Turner said.
"We may still be getting it, but hopefully we won't get bad, we won't end up in hospital and we certainly hopefully won't end up dead."