Influenza (Flu)

Page last updated: 23 July 2015

Influenza (flu) is a highly contagious viral infection that is responsible for major outbreaks of respiratory illness around the world, usually in the winter months. Unlike the common cold, influenza can cause severe illness and life-threatening complications such as pneumonia and bronchitis, which often require hospitalisation.

The flu virus is especially dangerous for elderly people, pregnant women, Aboriginal and Torres Strait Islander people and very young children, as well as for people with underlying medical conditions. It is estimated that each year, flu contributes to an average of 13,500 hospitalisations and more than 3,000 deaths among Australians aged over 50 years.


Three different types of influenza viruses infect humans: influenza A, B and C. Only influenza A and B cause major outbreaks and severe disease, and these are included in seasonal influenza vaccines. Influenza spreads from person to person through the air by coughing or sneezing, or by direct contact with the virus on hard surfaces or people’s hands. The flu usually differs from a cold as symptoms develop suddenly, and can lead to complications such as chest infections and pneumonia – particularly among the elderly and young children.


Flu symptoms tend to develop abruptly one to three days after infection, and can include: tiredness, high fever, chills, headache, coughing, sneezing, runny noses, poor appetite, and muscle aches. Most people who get the flu will suffer from mild illness and will recover in less than two weeks. However, some people can develop longer-term health problems, including pneumonia, bronchitis, chest and sinus infections, heart, blood system or liver complications, which can lead to hospitalisation and even death.


Vaccination offers effective protection against influenza, although vaccines need to be given each year as flu viruses are always changing.

National Immunisation Program 2015 seasonal flu shot

The 2015 flu shot is now available from GP surgeries and other immunisation providers. This YouTube video - It's time to think about getting the flu shot explains the 2015 seasonal influenza vaccination program.

The flu vaccine is recommended for everyone from six months of age, but is available free under the National Immunisation Program for people who face a high risk from influenza and its complications. These are:

To receive your influenza vaccination, visit your local doctor or immunisation provider. It is important to note that while the vaccine is free, a consultation fee may apply.

Influenza vaccination in children

Children can begin to be immunised against the flu from six months of age. Children aged eight years and under require two doses, at least four weeks apart in the first year they receive the vaccine. One dose of influenza vaccine is required for subsequent years and for children aged nine years and over.

All vaccines currently available in Australia must pass stringent safety testing before being approved for use by the Therapeutic Goods Administration (TGA).

Specific brands of flu vaccine are registered with the TGA for use in children. bioCSL flu vaccine Fluvax® is not registered for use in children less than five years of age and must not be given in this age group. In addition, the Australian Technical Advisory Group on Immunisation does not recommend the use of bioCSL Fluvax® in children aged five to nine years due to a potential increased risk of fever. However, febrile convulsions are rare in this age group. The use of bioCSL Fluvax® in children aged five to nine years should only be considered after careful review of the potential benefits and risks. A number of other flu vaccines are approved for use in these age groups.

Questions and Answers for Influenza (flu) immunisation

Three things you might not know about the flu shot:

  1. There is no live virus in the flu shot.
  2. The composition of the vaccine changes every year
  3. The flu shot is safe for pregnant women at all stages of their pregnancy.

I received a flu shot last year, do I still need to get one this year?

Yes. The strains of flu virus can change from year to year. The vaccine may also change to protect against the most recent flu virus strains. Even if the flu strains do not change, yearly vaccination is still recommended as immunity from flu vaccination is not long lasting.

Immunisation is recommended in early autumn to allow time for immunity to be strengthened before the flu season starts.

Is it safe for me to get the flu shot if I am pregnant?

Yes. The flu vaccine can be safely given during any stage of pregnancy. Pregnant women are at the increased risk of severe disease of complications from the flu. Immunising against flu during pregnancy can not only protect women but provide ongoing protection to a newborn baby for the first six months after birth.

Is it safe for me, as an adult to get the flu shot?

Yes. All flu vaccines currently available in Australia are safe to use in adults. All vaccines in Australia must pass stringent safety testing before being approved for use by the Therapeutic Goods Administration.

Further information on the safety of vaccines is available from the Therapeutic Goods Administration website.

What is the difference between the trivalent and quadrivalent flu vaccines?

The 2015 flu vaccine available under the National Immunisation Program is a trivalent vaccine. That means it protects against three strains of flu, two A strains and one B strain.

A quadrivalent influenza vaccine is also be available through the private market. The quadrivalent vaccine is expected to be at least as effective as the trivalent vaccine, and may offer additional benefit through protection against an additional influenza B strain. However, there is currently little information on the extent that this will result in additional benefit for patients. It is anticipated that the National Immunisation Program 2015 trivalent vaccine will offer good protection against the 2015 influenza season strains.

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