The Government has boosted flu vaccine supplies by 40 per cent as experts warn this season could be particularly bad because the country has far lower natural immunity.

New Zealand usually uses about 1.4 million flu vaccines a year.

Health Minister Andrew Little said this year two million would be available and more people could get vaccinated for free.

"With the Omicron wave still working its way through the country, we need to protect our most vulnerable from getting the flu as well, and our health system from coming under more pressure."

Already anybody over the age of 65 can get a flu jab for free, along with those who are pregnant or at risk of becoming seriously ill because of other underlying conditions.

This winter, under expert advice due to increased vulnerability, Māori and Pacific people aged 55 and over could also get the vaccine for free, which means an extra 39,000 people.

Little said as many people as possible should get the vaccine.

"In an ordinary year, flu kills more than 500 New Zealanders. And this is no ordinary year," he said.

Usually only half the people eligible for free vaccination took it up.

For the past two years, with the country closed to the rest of the world because of the Covid-19 pandemic, colds and flu had largely been kept out. But this year would be different.

"With our borders opening, I encourage everyone – and especially the most vulnerable – to get vaccinated.

"Anyone who is part of Group Three for the Covid vaccination rollout should make sure they get a flu shot.

The $12 million programme, funded from the Covid-19 response fund, starts across the country today, with vaccinations available from family doctors, pharmacists and some Māori and Pacific health providers.

Little said many new pharmacist vaccinators had been trained and authorised over the past two years, including provisional pharmacist vaccinators who are able to administer the influenza vaccine.

College of General Practitioners medical director and Porirua GP Dr Bryan Betty told RNZ this morning the influenza virus had barely been in New Zealand for two years, because of the closed border.

He said the flu was not a mild illness.

"The thing we need to understand about the flu - it's brought in from overseas by aeroplanes.

"New Zealand I think is particularly vulnerable because our borders were so closed we actually had no flu essentially in the country the last two seasons. As a result of that we think our natural immunity is down, which means we're far more susceptible to a bad flu season this year than perhaps we normally would be."

- by Michael Neilson, NZ Herald