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Page last updated on 17 February 2021

Seasonal influenza, also known as the flu, is an extremely contagious respiratory illness. In 2019, there were 313,085 (laboratory confirmed) cases in Australia, which was the largest since the 2009 pandemic year.

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 57 days after becoming sick, it can be difficult to control the spread of the virus .

If you are infected with the flu you can spread it to people up to 2 meters away.

Vaccination is one of the best ways to protect yourself against the flu and other complications associated with the flu, including pneumonia.

Key disease information

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

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


It 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.


The common cold is also caused by a virus, and also affects the airways, but generally tends to be milder than the flu. Colds do not usually cause serious complications or require hospitalisation.


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 severe disease appears to be higher for COVID-19.


So is it the flu, a cold or COVID-19? Often testing is required to know for sure, but here are some general ways you can distinguish some of the symptoms:






Symptom onset



Range from mild to severe










Fairly common











Stuffy nose




Sore throat




Chest discomfort, cough


Mild to moderate






Adapted from the Centers for Disease Control and Prevention (CDC ) and Australian Government, Department of Health.

How effective is the flu vaccine?

Each year, the flu vaccine effectiveness can vary – and it will depend on your age and other conditions and risk factors. It can also depend on the specific strains of influenza circulating in your community – the more closely they match the strains in the vaccine, the higher the effectiveness is expected to be.

It takes between 5 – 6 months to manufacture a next year’s influenza vaccine. 

Each year the World Health Organisation (WHO), along with a specific team of collaborating researchers, makes recommendations on which virus strains the influenza vaccine should cover for the following year. Once the vaccine strains have been decided, WHO then prepare the virus for use in manufacturing the vaccine. Once the vaccine has been tested to ensure it will protect against the specified strain, is safe and grows in eggs, it is then tested one last time and then sent to vaccine manufacturers for mass creation.

If you are unsure if the flu vaccine is suitable for you or your family speak with your health care professional for personalised advice.


Can I catch the flu from the vaccine?

No, and this is a common myth.

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

In some rarer situation people can develop some mild side effects associated with the flu vaccine. These 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 a yearly flu vaccine:

  • 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.
Why do doctors recommend getting a flu shot during pregnancy?

The flu is more likely to cause severe illness in pregnant women than non-pregnant women. Flu also may be harmful for a pregnant woman’s developing baby. A common flu symptom is fever, which may be associated with neural tube defects and other adverse outcomes for a developing baby.

The influenza vaccination given during pregnancy has been shown to protect both the mother and her baby for several months after birth from the flu.

For more information regarding influenza vaccination during pregnancy, speak with your healthcare professional.

When is the best time to get the flu vaccine?

Influenza season in Australia usually peaks in August or September each year. Optimal protection from influenza vaccination occurs in the first 34 months following vaccination. Therefore, it is recommended to vaccinate when the national program starts, which is generally in April. However as influenza continues to circulate, it is never too late to vaccinate.

If you are travelling to the northern hemisphere throughout their peak flu season, you should speak to your health professional about additional vaccination options.

Remember that it is always important to speak with your doctor about Influenza vaccination for you and your family.


Is the flu vaccine free?

Influenza vaccine is recommended for everyone > 6 months old.

It is currently free for the following groups of people due to their increased risk of complications from influenza:

  • All Aboriginal and Torres Strait Islander people
  • All adults ³65 years of age
  • All children ³6 months to <5 years of age
  • All people ³6 months of age with certain medical conditions (e.g. severe asthma, lung or heart disease, low immunity or diabetes) – speak to your doctor if you are unsure if you are eligible
  • Pregnant women (at any stage during their pregnancy).
How can the flu be prevented?

Annual vaccination is the best form of prevention. It is also important for everyone to take preventative measures on a day-to-day basis. People should always cover their face when coughing and sneezing. It is also recommended people sneeze into a tissue or their elbow, not directly onto hands, to prevent the spread of germs. Tissues should always be thrown into a rubbish bin after use. Hand washing is important too. Hands should always be washed with soap and water to help kill germs. Using an alcohol rub is also effective. If unwell with flu-like symptoms, it is advisable to stay at home to prevent the germs spreading in the workplace and the community.

VaccineHub offers general information only. Please see a healthcare professional for medical advice

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Sources & Citations

  1. National Notifiable Disease Surveillance System. Number of notifications of Influenza (laboratory confirmed), Australia, in the period of 1991 to 2019 and year-to-date notifications for 2020. Available at: (accessed 11 March 2020).
  2. Australian Technical Advisory Group on Immunisation (ATAGI). Australian Immunisation Handbook - Influenza. Available at: (accessed 11 March 2020).
  3. Centers for Disease Control. How Flu Spreads. Available at: (accessed 11 March 2020).  
  4. Australian Technical Advisory Group on Immunisation (ATAGI). Statement on administration of seasonal influenza vaccines in 2020. Available at: (accessed 11 March 2020).
  5. Centers for Disease Control. Cold versus flu. Available at: (accessed 11 March 2020).
  6. NSW Government. Health. COVID-19 - Frequently asked questions. Available at: (accessed 30 March 2020).
  7. Australian Government, Department of Health. COVID-19: Identifying the symptoms. Available at: (accessed 30 March 2020).
  8. World Health Organization. Influenza vaccine viruses and reagents. Available at: (accessed 11 March).
  9. World Health Organization. Pandemic influenza vaccine manufacturing process and timeline. Available at: (accessed 11 March 2020).
  10. Centers for Disease Control. Key facts about seasonal flu vaccine. Available at: (accessed 11 March 2020).
  11. Centers for Disease Control and Prevention. Pregnant women & influenza (flu). Available at: (accessed 11 March 2020).
  12. Young B et al. J Infect Dis 2018;217:731–741.
  13. NSW Government. Health. Influenza factsheet. Available at: (accessed 11 March 2020).

SPANZ.IFLU.18.04.0165(3) - Date of preparation March 2020