With the annual influenza immunisation campaign about to start, experts have laid out newer methods that could save lives - higher-powered vaccines for the elderly, and a nasal spray for children.

None of the newer vaccines are yet available in New Zealand. However, the Government's medicines buyer Pharmac said it had put out a request to the pharmaceuticals industry for proposals to supply the kinds of vaccines the experts want.

Influenza and its complications kill about 400 people a year in New Zealand. A 2015 study estimated that a quarter of the population caught influenza that year, most of them being disease carriers without symptoms who would have spread the virus without knowing.

Associate Professor Lance Jennings, an expert on viruses, said two influenza vaccines specifically for elderly people were available in Australia, but not yet in New Zealand.

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One is called Fluzone High Dose; compared with usual influenza vaccines it has four times the amount of antigen - the viral particles that induce an immune response.

The other is FluAd; it contains an adjuvant - an extra ingredient, in this case an oil-in-water emulsion - to strengthen the immune response.

Jennings said that although the overall effectiveness of influenza vaccine in New Zealand was about 60 per cent, it was less effective in the elderly because the immune system weakens with age.

Despite the lower effectiveness, he said vaccination was an older person's best protection against catching the disease and it also reduced the risk of influenza complications such as pneumonia and heart problems.

He said an older person admitted to hospital with influenza was on a "slippery slide" and tended never to regain their pre-illness level of activity.

Jennings expected the two vaccines for the elderly would be made available in New Zealand "in due course".

But Dr Nikki Turner, director of the Immunisation Advisory Centre at the University of Auckland, said there were questions about the cost-effectiveness of the vaccines for the elderly.

She would prefer New Zealand to follow Britain in offering a live, weakened-virus nasal-spray vaccine to all school children, an approach she said would reduce the spread of influenza in the whole community and consequently reduce the impact of the disease on the elderly.

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"School children are the main spreaders of influenza," Turner said.

Jennings predicted New Zealand would have a "moderate" influenza season this year, after a mild one last year.

He said A-H3N2 viruses, which tended to affect elderly people in greater numbers and led to more severe outcomes among them, were likely to predominate as they had during the New Zealand summer and in the latter part of the northern hemisphere's influenza season, now ending.

The annual state-funded influenza vaccination campaign starts on Monday.

The vaccine is free for pregnant women, people aged 65 or older, those aged 6 months to 65 who have any of a range of chronic health conditions, and children 6 months to 4 years who have been hospitalised for respiratory illness or have a history of significant respiratory illness.

Health authorities are aiming to vaccinate 25 per cent of the whole population, including 75 per cent of those aged 65 or older and 80 per cent of health workers.

Last year 1.3 million doses were distributed in the state-funded programme and this year the target is that the scheme will exceed 1.2 million doses. For others a flu shot costs around $35, although some people get one free through their workplace.

The state-funded vaccine will continue to have two influenza A strains and two B strains. One of the A strains - the H3N2 component - and one of the B strains have been changed since last year's vaccination programme.

Jennings said the changed strains "have been updated to be consistent with the dominant viruses in the northern hemisphere and those viruses likely to affect us in the coming winter".

Pharmac's immunisation subcommittee considered Fluad - a "tri-valent" vaccine active against three influenza strains - last year following an application by the supplier, Seqirus. It recommended against funding the vaccine at that time, stating that there were only limited head-to-head studies with other vaccines and none with a quadri-valent vaccine.

"Members considered that there was not sufficient evidence to support the use of aTIV [adjuvanted tri-valent influenza vaccine] at this time."

The United States Centres for Disease Control and Prevention, citing a study in the New England Journal of Medicine, says Fluzone High Dose tri-valent vaccine was found to be 24 per cent more effective at preventing influenza in adults 65 and older than Fluzone standard dose vaccine.

The agency says some adverse events were reported more frequently after Fluzone High-Dose than after injections with standard-dose vaccines. The main ones in studies were mild and temporary, and included pain, redness at the injection site, headache, muscle aches, and malaise. Most people had minimal or no adverse events after receiving the Fluzone High-Dose.