Key words

Vaccine	A product made from dead or weakened germs (bacteria or viruses) that helps your body learn how to fight the infection.
Vaccination	The process of getting a vaccine. Vaccination triggers immunisation in the body.
Immunity	The body’s ability to fight infection. This may happen after infection or after vaccination.
Immunisation	The process of becoming resistant to an infectious disease, usually through vaccination.
‘Booster’ dose	Extra vaccine doses given to strengthen immunity.

What is the immune system?

The immune system is how the body defends itself from infection.

It recognises ‘invaders’ such as bacteria, viruses and fungi and abnormal cells like cancer cells. It creates an immune response to help the body fight the invasion.

When harmful germs enter and invade the body, the body produces white blood cells to fight the infection. The white blood cells identify the germ and produce antibodies to fight it.

Antibodies are small proteins made by the white blood cells. Your immune system makes unique antibodies for each type of germ you are exposed to. Antibodies work by ‘sticking’ to a marker on the foreign germ cell, known as an ‘antigen’. Antibodies help your body identify which cells are foreign, so the immune system knows to attack them.

White blood cells also help with other immune responses, and can 'remember' the attack they have launched. ‘Remembering’ the attack is important, since it allows the body to respond more quickly if it is exposed to the same germ in the future.

Learn more about the immune system.

What is vaccination?

Vaccination prepares the immune system to fight against a future infection, without you becoming infected with the disease.

Antigens are markers on a foreign bacteria, virus or cell. Your immune system notices these antigens and creates a protein to help fight the invader, called an antibody.

Most vaccines have a small amount of antigen in them from dead or weakened germs. This helps your body learn how to fight the disease without you getting sick. This means that your body is better prepared to fight the disease if you are exposed again, as it already knows how to produce antibodies to target that germ.

Most vaccines are given by injection, but some are given orally (by mouth).

What is the difference between immunisation and vaccination?

Immunisation is when your body builds a defence to a disease.

Vaccination happens when you have the injection or take the oral vaccine dose.

Vaccinations are an important part of the immunisation process against many diseases.

How does immunisation work?

When you have a vaccine, your body creates an immune response. This is in the same way as if you had been exposed to the disease, but since you have only been exposed to a dead or weakened form of the germ, you won’t actually get sick.

If you are exposed to the disease in the future, your immune system will remember the disease faster. This helps your immune system act fast enough to stop you from having symptoms of the disease. Sometimes, it will not be fast enough to stop you from having symptoms altogether, but you will have a lower chance of becoming seriously ill.

How long do immunisations take to work?

It takes time for your immune system to respond to a vaccine, usually between 1 and 3 weeks.

The time it takes will depend on the vaccine you have, your age and general health.

This means that immunisation will not usually provide protection from infection straight away.

What is in vaccines?

All vaccines have the same purpose, but their contents may vary depending on the germ they target. Vaccines may contain tiny doses of:

• a weakened form of a virus
• dead bacteria or small parts of bacteria
• a modified toxin made by the bacteria

Some vaccines contain instructions that ‘teach’ your body how to fight an infection.

Vaccines may also contain a small amount of preservative or traces of other substances such as antibiotics, egg or yeast proteins. These components may be left over from the vaccine manufacturing process, or they may be added to increase the shelf life of the vaccine.

Some vaccines also contain a small amount of an aluminium salt to help produce a better immune response.

What’s the difference between a booster dose and a primary vaccine course?

A primary vaccine course has the number of doses you need for strong protection against a disease.

A booster dose is an extra dose of a vaccine given many months or years after you’ve had the primary vaccine course. It gives your immune system a 'boost', and gives you extra protection from the disease.

For example, you may have a booster dose for tetanus and whooping cough (pertussis).

How many doses of vaccine do I need to be protected?

How long do immunisations last?

Immunisation doesn’t always last for your whole lifetime.

For example, the tetanus vaccine can last up to 10 years. After this time, you will need a booster dose to restore your immunity.

A new influenza immunisation is released each year. The flu virus changes each year, so the vaccine is updated regularly.

Is everyone protected from disease by immunisation?

Reducing your chance of disease

Immunisation greatly increases your immunity against disease, but there is still a small chance that you will get sick. For example, most childhood vaccines will give strong protective immunity to about 9 out of 10 children who have had the recommended number of doses.

Reducing other people’s chance of disease

High vaccination rates make these diseases less common in the community. This means even someone who is not vaccinated is less likely to catch the disease. This is called ‘herd immunity’.

Herd immunity is important for people who can’t be or aren’t yet vaccinated, especially:

• babies and children who are too young for some vaccines
• babies and children who are still not fully vaccinated
• people who are allergic to some components of a vaccine
• those with a weakened immune system

When you become immunised, you reduce the chance that these people will catch the disease.

Will immunisation stop me from becoming sick?

Some vaccines won’t necessarily stop you from catching the disease, but they will reduce your chance of serious illness. An example is the COVID-19 vaccine.

It’s still important to have these vaccines as they reduce the chance of serious illness if you do get sick.

Other vaccines, such as the vaccine for whooping cough, prevent disease in most people.

How are vaccines approved in Australia?

Before a vaccine becomes available in Australia it must be approved by the Therapeutic Goods Administration (TGA). This is a strict process that includes assessing every ingredient in the vaccine for safety, quality and effectiveness.

The TGA looks carefully at clinical trials to see if the vaccine is effective and safe. Clinical trials of medicines are done in phases.

The TGA ensures that makers of vaccines meet manufacturing quality standards. TGA laboratories also check the quality of every batch of a vaccine before it can be used in Australia.

Sometimes a ‘provisional approval pathway’ is needed. This allows for temporary registration of promising new medicines and vaccines. This is only done where the need for early access is considered greater than any possible risks.

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Resources and support

In Australia, vaccines are funded by the National Immunisation Program and protect millions of Australians from vaccine-preventable diseases.

If you have any questions, you can speak to your doctor or call healthdirect on 1800 022 222 (known as NURSE-ON-CALL in Victoria).

Languages other than English

The Department of Health, Disability and Aging has resources on childhood immunisation available in a range of community languages.

Information for Aboriginal and/or Torres Strait Islander peoples

The Department of Health, Disability and Aging has a collection of childhood immunisation resources for Aboriginal and Torres Strait Islander people.

The Queensland government has a Bubba Jabs poster showing when your child’s vaccinations are scheduled.