Wanganui people are being urged to call their doctor or nurse as soon as possible to book their flu vaccination before winter.
The yearly vaccinations are free for many people.
Influenza or "flu" can be a serious illness because it is more than a "bad cold".
Dr Lance Jennings, virus expert and spokesman for the National Influenza Specialist Group (NISG) said anyone could catch the flu and even fit and healthy people could get it and become very sick.
"Some people can end up in hospital and some die because the disease can make other conditions, such as breathing or heart problems, even worse," Dr Jennings said.
Flu immunisation is free for New Zealanders at high risk of more severe disease and complications. This group includes pregnant women, people aged 65 and over, and anyone with ongoing health conditions such as heart disease, strokes, diabetes, respiratory disease (including asthma), kidney disease and most cancers.
Last year, 74 per cent of over-65s were vaccinated across the Whanganui District Health Board region. The national target was 75 per cent.
Dr Jennings said the seriousness of influenza should not be underestimated. "Even a moderate dose of flu can stop you from working, studying or enjoying other activities for a week or more. And some people feel tired for weeks afterwards."
Influenza vaccine is only free for eligible groups from a doctor or nurse until July 31. The vaccine is available to other people for a small charge. Immunisation is also available - but not free - for healthy children six months and over and adults.
Influenza is caused by a viral infection that affects the respiratory system and between 10-20 per cent of the population are infected with influenza each year.
Dr Jennings said influenza immunisation could not give you the flu because it did not contain live viruses. But he said there could be side effects, and these usually disappeared within one or two days without treatment.
"Most reactions from the vaccine are very mild and usually consist of pain, and sometimes redness or swelling at the injection site," he said.
"As well as getting a flu vaccination you may protect yourself and your family from flu if you wash and dry your hands often, stay away from people who are sick, stay away from work or school if you're unwell and cover your coughs and sneezes.
For further information go to www.fightflu.co.nz or www.moh.govt.nz or call 0800 IMMUNE 0800 466 863.