Health professionals are expecting a fourth Covid-19 vaccine dose will be less popular in its uptake.

A second booster - or fourth dose - is now available for everyone aged over 50, as well as health, aged-care and disability workers over the age of 30.

The Ministry of Health recommends people stay up-t- date with vaccinations but significantly fewer people have received their first booster dose than the first two jabs.

Only 72.9 per cent of the total eligible population have received a first booster shot, equating to 987,833 eligible people not receiving it.

A number of eligible people questioned by RNZ wanted a fourth dose but did not know it was available.

One man says he will have "probably expected to know" before being asked by RNZ because the announcement was made hours beforehand.

Another man says that "it always must be of concern" that a public health measure appear to not have reached its intended audience.

Similarly, Rotorua-based GP Cate Mills says she knew an announcement was imminent but did not know it had happened until contacted by RNZ.

She now can have patients ask for it today and has previously had some enquire.

Rotorua is in the Lakes District Health Board area, where just over 67 per cent of eligible people have had the first booster shot.

It is the second worst rate among DHBs for boosters, slightly above its neighbour Bay of Plenty (other DHBs have worse first and second dose rates).

With more than a quarter of people nationally who turned up for the first two Covid-19 vaccinations not returning for a third, Mills expected those eligible would be even less interested in a fourth dose.

"It might only be 50 percent," she says.

Call for a shorter wait time

Otago University epidemiologist Nick Wilson is expecting more than half of those eligible for the fourth dose to take it.

"I would hope it would be much higher."

He wants people to get vaccinated to keep them out of hospital and help ease the strain on the health system.

But he says many may only be able to get the fourth dose once winter is over - noting people are not supposed to get the jab within three months of having Covid-19 and must wait six months after their last shot.

Wilson says the six-month wait should be shortened "maybe even down to three or fourth months".

He suggests decisions around that could wait until officials saw what the actual fourth dose uptake is like.

Pasifika GP Network chair Dr Api Talemaitoga wants to be optimistic but ultimately thinks there is Covid-19 fatigue and convincing people to get a fourth dose will be a "hard sell".

"People are tired of hearing about the Covid messages," he says.

"A lot of people have had Covid in Aotearoa and may think 'that's enough - I don't need to have the booster shot because I've already had Covid'."

Talemaitoga says officials can't leave it to medical professionals to get the message out because they are already exhausted.

He says vaccination need to be clearly available and accessible.

"I know it's going to be hard but that doesn't mean we should not try and still get as many of ourselves boosted with another dose."

A Ministry of Health spokesperson says most of those in the fourth dose group will be over their six-month wait in July and August.

The ministry is planning to run an advertising campaign as well as directly contacting people when they become eligible.

Covid-19 Response Minister Ayesha Verrall says the criteria for who can be boosted will continue to be reviewed.

She says the message remains for young and old to get vaccinated when they can to protect themselves and others.

-RNZ/Jake McKee,.