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Seasonal influenza, also known as the flu, is an extremely contagious respiratory illness.

Page last updated 16 November 2023

Both 2020 and 2021 have seen lower numbers of influenza cases due to the COVID-19 pandemic and the public health measures that were implemented to help reduce the spread of illness. In 2020, there were 21,266 notifications of influenza and 598 in 2021. While these numbers are low, there were record numbers of confirmed influenza cases reported in 2017 (233,453) and 2019 (313,033).

There are three main types of flu virus: the A, B, and C strain. The A and B strains cause most influenza in Australia. Each year the strains circulating are different. In some years, one of the A strains may be more common, while in other years, the B strains may be more common. The flu is generally spread by coming in contact with an infected person, through droplets made when they talk, cough and sneeze. As a healthy person can begin infecting others from as early as 1 day before symptoms develop, and up to 5–7 days after becoming sick, it can be difficult to control the spread of the virus.

Influenza can disrupt your life. If you become sick with influenza, you might:

  • Have to stay in bed for several days
  • Need to take time off work, resulting in financial hardship
  • Miss out on important life events (birthdays/weddings)
  • Develop complications like pneumonia and end up in hospital

Influenza can cause serious respiratory illness, especially in more vulnerable members of our community. The influenza vaccine is the simplest and most effective way to prevent influenza and its complications like pneumonia. The Department of Health recommends influenza vaccination for everyone over the age of 6 months to prevent influenza and its complications. 

For further information regarding vaccination against influenza, speak with your healthcare professional.

Video: How does Influenza link to Cardiovascular Disease

Commonly asked questions

What is the difference between the flu, a cold and COVID-19?

Influenza, the common cold & COVID-19 are all contagious respiratory illnesses. Whilst they share similar symptoms, they are caused by different viruses.

Influenza are a group of viruses that are responsible for the disease we commonly call the 'flu'.  

With a cold you generally only experience mild symptoms like a runny nose. But influenza and COVID-19 can cause serious respiratory illness and can lead to severe complications like pneumonia.

Influenza is a disease that is spread from person to person during coughing or sneezing or by direct contact with respiratory secretions (e.g. saliva, nasal discharge). It can cause a wide range of disease, from mild to more severe disease that affects many body systems and can result in hospitalisation, other infections (e.g. pneumonia) and even death.

COVID-19 comes from a large family of viruses called coronaviruses. It is transmitted in the same way as the flu, with similar symptoms, but overall COVID-19 appears to cause more serious illnesses in some people.

So is it the flu, a cold, allergies or COVID-19? It’s important to be aware of the symptoms and to get tested if you become sick to confirm your diagnosis. Here are some general ways you can distinguish some of the symptoms:


(ranging from
mild to severe



(onset can be
gradual or
Fever Often Rarely Often No
Cough Often Often Often Common
Sore Throat Sometimes Often Sometimes Sometimes
(itchy throat & palate)
Shortness of breath Sometimes No No Common
Fatigue Sometimes Sometimes Often Sometimes
Aches & pains Sometimes No Often No
Headaches Sometimes Often Often Sometimes
Runny or stuffy nose Sometimes Often Sometimes Often
Diarrhoea Rarely No Sometimes
(especially in children)
Sneezing  No Often No Often

Adapted from Australian Government, Department of Health (COVID-19: Identifying the symptoms).

How effective is the flu vaccine?

Each year, the flu vaccine effectiveness can vary. It will depend on many factors such as your age, health status, and how closely the specific virus strains in the vaccine match those circulating in your community.


For further information about flu vaccination and which flu vaccine is suitable for you or your family, speak with your doctor, nurse or pharmacist for personalised advice.

How is it decided which influenza strains to include in the vaccine?

Each year the World Health Organization (WHO), along with a specific team of collaborating researchers, makes recommendations on which virus strains the influenza vaccine should include for the following year. They do this by monitoring which virus strains are circulating around the world, and making a prediction on which strains will circulate the following season.

Once the vaccine strains have been decided, WHO then prepare the virus for use in manufacturing the vaccine. The vaccine will undergo multiple tests to ensure it will protect against the specified strain and is safe for use. Then these strains are sent to vaccine manufacturers for mass creation. It usually takes between 5 – 6 months to manufacture an influenza vaccine.

For further information about flu vaccination,  speak with your doctor, nurse or pharmacist.

Can I catch the flu from the vaccine?


The flu vaccine cannot cause influenza disease as they are made from inactivated (dead) viruses.

After an influenza vaccination, some people can develop mild, short-lived side effects which can include:

  • Soreness, redness or swelling at the site of the injection
  • Fever
  • Aches


Why do I need to get vaccinated against the flu each year?

There are two main reasons for getting an influenza vaccine every year, to give you the best protection:

  • Flu viruses are frequently changing and vaccines may be updated from one season to the next to protect against the most recent and common circulating strains
  • A person’s immune protection from influenza vaccination declines over time and annual vaccination is recommended.

Sources & Citations

  1. Department of Health. Australian Influenza Surveillance Report – 2020 National Influenza Season Summary. Available at: (accessed 23 November 2021).
  2. Department of Health. Australian Influenza Surveillance Report – 2021 National Influenza Season Summary. Available at:
    ozflu-flucurr.htm#current (accessed 23 November 2021). 
  3. Department of Health. 2017 influenza season in Australia. Available at:$File/2017-season-summary-22112017.pdf (accessed 26 November 2021).
  4. National Centre for Immunisation Research and Surveillance. Influenza vaccine for Australians. Available at: (accessed 23 November 2021). 
  5. Department of Health. Australian Immunisation Handbook - Influenza. Available at: (accessed 10 November 2021). 
  6. World Health Organization. Influenza (seasonal). Available at: (accessed 23 November 2021).

MAT-AU-2102448  Date of preparation December 2021