What is it?

Influenza viruses are single stranded RNA orthomyxoviruses which can cause acute viral infections of the respiratory tract. Infections are often classified according to the type of influenza virus responsible for the infection, typically A, B, or C. Influenza types A and B are more commonly responsible for causing severe disease. Influenza A can be further subtyped based on the differences in surface antigens.

What to look for

The incubation period of influenza disease is 1-4 days with typical symptoms including fever, headache, myalgia (muscle aches), lethargy (tiredness), coryza (runny nose), sore throat and cough. Gastrointestinal symptoms such as nausea, vomiting and diarrhoea can also occur. Children with influenza will often present with symptoms of croup.

Most influenza infections will resolve within 2-7 days. However, complications including otitis media (ear infections), secondary bacterial pneumonia (lung infections) and encephalitis (brain inflammation) can prolong the illness and disease outcomes.

How is it transmitted

Influenza is highly contagious. Transmission is via respiratory droplets, aerosol or through direct contact with the respiratory secretions of an infected person.


Influenza disease can occur as sporadic cases, as an epidemic, or as a pandemic. Whilst outbreaks more commonly occur in the winter months in temperate climates, there is a greater variation seen in the timing of cases in the tropics.

Aged care facilities, health care facilities and child care centres are well recognised as high-risk areas for influenza outbreaks.

Pregnant people, children < 5 years of age, those aged > 65 years, people with underlying medical conditions, and Aboriginal and Torres Strait Islander peoples carry the highest rates of morbidity and mortality within Australia.


Influenza vaccination is available and recommended for anyone ≥ 6 months of age who wishes to be protected against influenza disease and its complications. Due to the circulating strains of influenza virus changing each year, vaccination is recommended annually to provide the most effective protection against disease. 

Influenza vaccines are provided for free on the National Immunisation Program (NIP) in 2024 for high-risk groups, including: 

  • children aged 6 months to < 5 years 
  • all adults ≥ 65 years of age 
  • specific populations aged 5 years to 64 years who are at a greater risk of developing complications from influenza (including pregnant people, First Nations people, and those with certain medical risk factors). 

Those aged 5 to 64 years who do not qualify for funded vaccines can purchase vaccines privately through some councils, GPs and pharmacies.

Vaccine platform

The influenza vaccines available in Australia are inactivated, meaning that they cannot replicate and cause influenza disease. They can be cell-based or egg-based depending on how they are manufactured. 

Traditional influenza vaccines are made by cultivating influenza viruses in chicken eggs. Cell-based influenza vaccines are made by growing influenza viruses in animal cells lines (canine kidney). ATAGI has no preference for use of cell-based influenza vaccines over traditional egg-based vaccines (individuals with egg allergy/anaphylaxis can safely receive egg-based influenza vaccines, see commonly asked questions below).

Table 1: The influenza virus strains included in the 2024 seasonal influenza vaccines 

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Whilst the World Health Organization (WHO) and the Australian Influenza Vaccine Committee (AIVC) recognise that the B Yamagata strain has not been circulating for several years and its inclusion in annual vaccines is no longer warranted, it has been included in the 2024 influenza vaccines. This is not a safety concern and WHO and the AIVC support its inclusion (refer to resources below). 

Adjuvanted and high-dose vaccines

Due to a gradual decline in effectiveness of the immune system of older people (a process known as immunosenescence) immunity following vaccination with standard influenza vaccines can be suboptimal. In addition, those aged ≥ 65 years have the highest rates of influenza disease burden and associated complications including pneumonia and death. Therefore, to increase the immune response adjuvanted (Fluad Quad) or high-dose (Fluzone High-dose Quad) influenza vaccines are the preferred vaccine type for the older population.

Table 2: The 2024 influenza vaccine brand recommendations according to age

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* 2 doses, minimum of 4-weeks apart should be given to children < 9 years of age in the first year of receiving the influenza vaccine, a single dose is recommended in subsequent years.
ΩNIP funding only for First Nations people, pregnant people and people with certain medical risk factors
#Adjuvanted or high-dose quadrivalent influenza vaccines are preferentially recommended for people adults ≥ 65 years.
βFluarix-tetra/FluQuadri/Afluria Quad/Vaxigrip tetra/Influvac tetra/ Flucelvax Quad are registered for use in people aged ≥ 65 years, however adjuvanted or high-dose vaccines are the preferred vaccines for this age group.
^2 doses are recommended in the first year following solid organ transplant (SOT) or haematopoietic stem cell transplant (HSCT) regardless of history of influenza vaccination due to immunosuppression. The exception to this is in individuals receiving an adjuvanted or high-dose influenza vaccine where only 1 dose is recommended.
shaded boxes indicate vaccines funded under the NIP for eligible individuals.
shaded boxes not registered for use in this age group.
shaded boxes indicate adjuvanted or high-dose vaccines.

Expected side effects

Common side effects following vaccination include pain, redness and swelling at the injection site as well as fever, malaise and myalgia. Symptoms usually occur within the first 24-48 hours following immunisation.

Cell-based influenza vaccines have a similar side-effect profile to traditional egg-based influenza vaccines. Side effects may occur slightly more commonly following immunisation with adjuvanted quadrivalent formulations than with standard influenza vaccine formulations.

Commonly asked questions

When is the ideal time to be immunised against the flu?

Annual vaccination before the onset of influenza season is recommended for all individuals ≥ 6 months of age. The peak period of circulating influenza disease in Australia is typically June to September. However, out of season cases can and do occur. Optimal protection against influenza occurs within the first 3-4 months following vaccination. It is never too late in the season to vaccinate.

Pregnant women can safely receive the influenza vaccine during any stage of pregnancy. Where a pregnancy crosses over seasons, some pregnant women may be recommended to receive 2 influenza vaccines, one from each year.

Do healthy people need to be immunised against influenza?

Influenza can be a very serious disease resulting in hospitalisation and death. Even in cases where disease and its complications are not severe, it can cause a great inconvenience for the individual, including the cost of GP visits and medications, as well as time off work for themselves or to care for their sick child.

In some cases, a person may not get severe disease but infection can be spread to other people. This can be significant when it is spread to those who are too young to be immunised or are at higher risk of complications of disease.

If an individual has had confirmed influenza disease this year, are they still recommended to receive an influenza vaccine and when should they receive it?

Vaccination is still recommended for someone with a history of confirmed influenza infection as the vaccine protects against multiple strains of influenza disease. The influenza vaccine can be administered as soon as the patient has recovered from their illness.

Can the influenza vaccine be given at the same time as other vaccines?

Yes, influenza vaccines may be co-administered with any other vaccine on the same day. This includes live-attenuated vaccines (e.g. measles and varicella) and the pertussis vaccine in pregnancy.

If a patient received a 2023 influenza vaccine at the end of the season in early 2024, do they still need a 2024 influenza vaccine?

Yes. A 2024 influenza vaccine is still recommended in order to provide protection against this year’s circulating strains. A minimum interval of 4 weeks is recommended.

In children < 9 years of age who received the influenza vaccine for the first time last year but only received 1 dose, how many doses are required this year?

Only 1 dose is required in this instance. 2 doses of the influenza vaccine are recommended for children < 9 years of age in the first year of receiving the vaccine. However, if the second dose was inadvertently missed, it does not require catch up and only 1 dose is required in future years.

Are influenza vaccines safe for people with allergies?

Based on prospective and retrospective studies of influenza vaccination in those with and without egg allergy (including egg anaphylaxis), the presence of egg allergy does not increase the risk of allergic reactions to the influenza vaccine. Egg-based influenza vaccines can be administered in community vaccination clinics (which may or may not have direct medical practitioner supervision), General Practitioner surgeries or immunisation clinics as a single dose followed by the recommended 15 minute observation period. It is not necessary to preferentially administer cell-based influenza vaccines in this patient group.

All influenza vaccines available under the NIP in 2024 are latex free meaning that people with a latex allergy can safely be vaccinated.

Authors: A/Prof Nigel Crawford (Director SAEFVIC, Murdoch Children’s Research Institute), Rachael McGuire (Research Nurse SAEFVIC, Murdoch Children’s Research Institute), Georgina Lewis (Clinical Manager SAEFVIC, Murdoch Children’s Research Institute) and Mel Addison (Research Nurse SAEFVIC, Murdoch Children’s Research Institute).

Reviewed by: Rachael McGuire (MVEC Education Nurse Coordinator).

Date: March 2024

Materials in this section are updated as new information becomes available. The Melbourne Vaccine Education Centre (MVEC) staff regularly review materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.