Influenza, commonly known as the flu, is caused by a highly contagious virus that is spread by contact with fluids from coughs and sneezes. Every year, the flu causes widespread illness in the community. Annual immunisation is strongly recommended for older people and other people who are at risk of serious complications from the flu (such as pneumonia).
An influenza epidemic occurs when an outbreak of the illness is widespread in a certain community. A pandemic occurs when the illness is more geographically widespread and on more than one continent. Influenza epidemics occur, on average, every three years whereas pandemics have occurred only four times in the past 100 years.
Annual immunisation against the flu is strongly recommended for people in at-risk groups such as older people, pregnant women and those who work or live with people in at-risk groups. Annual influenza vaccination is recommended for any person from six months of age who wishes to reduce the likelihood of becoming ill with the flu.
Immunisation against the flu
Immunisation of people who are at risk of complications from the flu is the most important way we have to reduce the number of flu infections and deaths.
Influenza viruses change every year because the influenza virus has a unique ability to change its surface structure. This means that even if you had the flu or an immunisation one year, your body’s immune system might be unable to fight the changed version of the virus that will be circulating the following year.
Each year, a new vaccine is developed (usually called the seasonal vaccine) and is available for those who wish to be immunised. The seasonal influenza vaccine includes protection against four strains of influenza.
Recent evidence suggests protection against influenza may start to decrease from three to four months following vaccination. Annual vaccination before the onset of each influenza season is recommended. While influenza continues to circulate, it is never too late to vaccinate.
The influenza vaccine cannot give you a dose of flu because it does not contain live virus. Some people may still contract the flu because the vaccine may not always protect against all strains of the influenza virus circulating in the community.
An annual flu vaccination is provided through the National Immunisation Program for most people in the community who are considered to be at an increased risk of complications. In Victoria, an annual vaccination against the flu is free for:
- all Victorian children aged six months to less than five years of age
- people who have medical conditions that put them at risk of serious complications of the flu
- Aboriginal and Torres Strait Islander people aged six months to under five years and 15 years and over
- pregnant women – at any stage of pregnancy
- people 65 years and over.
Contact your doctor or immunisation provider for further information about eligibility. People not covered by these categories can also have an annual flu immunisation but it is not available for free.
People who should be immunised against the flu
People with an underlying medical condition or reduced immunity are most at risk and should be immunised against the flu. They include:
- anyone aged 65 years and older
- pregnant women (at any stage of pregnancy)
- Aboriginal and Torres Strait Islander people aged six months to under five years and 15 years and over
- people aged six months or older with:
- heart disease
- chronic lung disease (including people with severe asthma who require frequent hospital visits)
- chronic neurological conditions
- impaired immunity
- haemoglobinopathies (blood disorders caused by genetic changes)
- kidney disease
- children on long-term aspirin therapy aged 6 months to 10 years.
Immunisation is also recommended (but not necessarily free) for people who can put vulnerable people at risk of infection. People who work with or live in close contact with people who have an underlying medical condition or impaired immunity should also be immunised to minimise the spread of the flu to themselves, the people they work or live with and their families. These people include:
- health care workers who provide direct care to people
- people with Down syndrome
- people who are obese (BMI greater than or equal to 40 kg/m2)
- people who are addicted to alcohol
- people who are homeless
- residents in nursing homes or other long-term care facilities
- staff in long-term care facilities or nursing homes
- people who live with, or care for someone who has a chronic illness or is aged over 65 years
- carers of homeless people
- workers, particularly those in workplaces that provide essential services
- people who work with children
- people involved in the commercial poultry and pig industry
- workers in other high-risk industries
- anyone visiting parts of the world where flu is circulating, especially if travelling in a group.
Some workplaces run annual immunisation programs for staff.
Flu vaccines for different ages
Age restrictions apply to all influenza vaccine brands. There is a formulation for children under three years of age and stronger formulations for people aged 65 years and older. Check with your immunisation provider that the right formulation is used for you or your child.
Pregnancy and immunisation
Pregnant women are at increased risk of complications from the flu. Influenza vaccine is strongly recommended and safe for pregnant women at any time during pregnancy. It can also be safely given while breastfeeding.
Influenza vaccination of pregnant women also protects infants against influenza for the first six months after birth due to transplacental transfer of antibodies from the vaccinated woman to the fetus.
Influenza pre-immunisation checklist
Before receiving the vaccine, make sure that you tell your doctor or nurse if you (or your child):
- are unwell (have a temperature over 38.5ï‚°C)
- have allergies to any other medications or substances
- have had a serious reaction to any vaccine
- have had a serious reaction to any component of the vaccine
- have had a severe allergy to anything
- are under six months of age
- have had Guillain-Barré syndrome.
Side effects of the flu vaccine
The influenza vaccine can cause a range of side effects. In children under five years of age, these reactions may be more obvious. Common side effects of flu vaccine include:
- drowsiness or tiredness
- muscle aches
- localised pain, redness and swelling at the injection site
- occasionally, an injection-site lump (nodule) that may last many weeks but needs no treatment
- low-grade temperature (fever).
Managing fever after immunisation
Common side effects following immunisation are usually mild and temporary (occurring in the first two days after vaccination). Specific treatment is not usually required. There are a number of treatment options that can reduce the side effects of the vaccine including:
- drinking extra fluids and not overdressing if there is a fever
- although routine use of paracetamol after vaccination is not recommended, if fever is present, paracetamol can be given – check the label for the correct dose or speak with your pharmacist, (especially when giving paracetamol to children)
Concerns about side effects
If the side effect following immunisation is unexpected, persistent or severe, or if you are worried about yourself or your child’s condition after a vaccination, see your doctor or immunisation nurse as soon as possible or go directly to a hospital.
Immunisation side effects may be reported to the Victorian Vaccine Safety Service (SAEFVIC), the central reporting service in Victoria on 1300 882 924 (option 1). You can discuss how to report problems in other states or territories with your immunisation provider.
It is also important to seek medical advice if you (or your child) are unwell, as this may be due to other illness rather than because of the immunisation.
Rare side effects of the flu vaccine
There is a very small risk of a serious allergic reaction (anaphylaxis) to any vaccine. This is why you are advised to stay at the clinic or medical surgery for at least 15 minutes following vaccination in case further treatment is required. Apart from anaphylaxis, other extremely rare side effects include febrile convulsions in children.
A small increase in Guillain-Barré syndrome was seen in the US in 1976, but since that time, surveillance has shown that it is limited to one case for every million doses of flu vaccine, if at all.
If any other reactions are severe and persistent, or if you are worried, contact your doctor for further information.
Immunisation and HALO
The immunisations you may need are decided by your health, age, lifestyle and occupation. Together, these factors are referred to as HALO.
Talk to your doctor or immunisation provider if you think you or someone in your care has health, age, lifestyle or occupation factors that could mean immunisation is necessary. You can check your immunisation HALO using the downloadable poster.
Where to get help
- Your doctor
- In an emergency, always call triple zero (000)
- Emergency department of your nearest hospital
- Your local government immunisation service
- Maternal and Child Health Line (24 hours) Tel. 132 229
- NURSE-ON-CALL Tel. 1300 60 60 24 – for expert health information and advice (24 hours, 7 days)
- Immunisation Program, Department of Health and Human Services, Victorian Government Tel. 1300 882 008
- National Immunisation Information Line Tel. 1800 671 811
- Victorian vaccine safety service (SAEFVIC) Tel. 1300 882 924 (option 1) – the line is attended between 9 am and 4 pm and you can leave a message at all other times
This page has been produced in consultation with and approved by:
Department of Health and Human Services - RHP&R - Health Protection - Communicable Disease Prevention and Control Unit
Content on this website is provided for education and information purposes only. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your doctor or other registered health professional. Content has been prepared for Victorian residents and wider Australian audiences, and was accurate at the time of publication. Readers should note that, over time, currency and completeness of the information may change. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions.