What are vaccines?

Vaccines are medicines that help to protect you and your family from infectious diseases by boosting your immune systems.

We need vaccines because some infectious diseases can make people very sick. They can even kill people.

Vaccines also stop infectious diseases spreading in the community.

How does the immune system work?

The immune system is your body’s natural defence system. When you’re exposed to a virus or bacteria, your immune system makes antibodies to fight the virus or bacteria.

The first time you’re exposed to a virus or bacteria, the immune system can be slow to make antibodies. That’s because it doesn’t recognise the virus or bacteria. While your immune system is making new antibodies, the virus or bacteria multiplies and spreads throughout your body. This is what causes disease symptoms – for example, fever, cough or rash.

Once your immune system has produced antibodies, it starts to destroy the virus or bacteria. And you start to recover from disease symptoms.

Your immune system also makes memory cells when you’re exposed to a virus or bacteria. If you’re exposed to the same virus or bacteria again, your immune system can respond quickly because these cells remember how to make the right antibodies. And this means you get only mild disease symptoms or no symptoms at all.

How do vaccines give you immunity?

Vaccines boost your immune system’s ability to fight viruses or bacteria, but you don’t have to get the viruses or bacteria first.

Vaccines are made with dead or weakened viruses or bacteria, or the genetic code or protein from viruses or bacteria. This allows vaccines to ‘trick’ the immune system into producing antibodies. But because you haven’t actually been infected by the virus or bacteria, you get no disease symptoms or only mild symptoms.

But if you’re exposed to a real virus or bacteria, the antibodies already in your body are ready to fight the virus or bacteria straight away. Your memory cells are also ready to quickly make more antibodies.

You need a certain level of antibodies and memory cells to protect you from viruses and bacteria. So you might need several doses of a vaccine over time to keep your antibodies and memory cells at a level that gives you ongoing protection from disease.

Vaccines contribute to herd immunity. Herd immunity is when enough people in the community are protected from a disease, and the spread of the disease either slows down or stops completely. Herd immunity protects everyone, including vulnerable people who might not be able to get vaccinated because they’re too young or have a serious illness or weak immune system.

Why is vaccination better than infection?

Getting vaccinated is much better than getting an infectious disease.

Vaccines, like all medicines, can give you side effects. But these are usually mild and go away quickly. For example, you might get a fever,  pain or skin discolouration where the vaccine is injected. Serious side effects from vaccines are extremely rare.

Vaccines can’t give you an infectious disease.

But you can get infectious diseases if you’re not vaccinated. And infectious diseases can make you very sick, cause you permanent disability, or even kill you.

Not all vaccines are completely effective. For example, the chickenpox vaccine is about 90% effective. This means that some people who are vaccinated might still get disease symptoms if they’re exposed to the chickenpox virus. But if this happens, people get less severe symptoms and usually recover more quickly.

What vaccines do children need?

Babies and young children get many vaccines through the National Immunisation Program. The best time to get a vaccine is before you’ve been exposed to an infectious disease, so that’s why children get so many vaccines during childhood.

It’s also important for children to get vaccines during childhood because children have strong immune systems. This means they have strong immune responses to vaccines, which gives them a lot of protection against infectious diseases.

For the best protection against diseases, babies and children need to get vaccines at particular times during childhood. They might also need to get doses of the vaccines several times.

But there are some diseases that aren’t a big risk for young children, so children can get vaccines for these diseases when they’re older. Human papillomavirus is a good example. Children get this vaccine when they’re aged 12-13 years.

What vaccines do women need during pregnancy and breastfeeding?

It’s recommended that pregnant and breastfeeding women get influenza, whooping cough, respiratory syncytial virus (RSV) and COVID-19 vaccines. These vaccines can protect women from these diseases, and the vaccines also protect their babies. For example, if you get the whooping cough or RSV vaccine in pregnancy, your baby gets antibodies. These antibodies protect your baby from whooping cough and bronchiolitis until your baby is old enough to get the vaccine.

Some infectious diseases, like rubella, measles and chickenpox, can harm unborn babies. But it isn’t safe for pregnant women to get the vaccines for these diseases. This is why it’s important for women to be up to date with vaccines before they get pregnant.

What vaccines do people with weak immune systems need?

Some people have weak immune systems. This includes people with medical conditions like cancer or people who are taking medicines like chemotherapy or corticosteroids. These people can’t fight infectious disease in the same way as healthy people.

It’s very important for these people to be protected against diseases, but vaccination can be complicated for them. They might need extra vaccines or extra doses to make sure that the vaccine works properly.

There are also some vaccines that people with weak immune systems shouldn’t have, like the measles, mumps and rubella vaccine.

How do vaccines affect people with allergies?

Adults and children with allergies to things like dairy or nuts can usually have vaccines.

Allergies to vaccines are very rare. These allergies must be diagnosed by an allergy specialist.

People who’ve had an anaphylactic reaction to a vaccine or an ingredient in a vaccine in the past shouldn’t get the vaccine.

What vaccines do older people need?

Older people have weaker immune systems than young people. Their immune responses to infections and vaccines are weaker than those of children and younger adults. This means vaccines might not work as well in older people.

Older people might need extra vaccine boosters or specific vaccines to ensure that their immune response is strong enough to protect them from infectious diseases.

If a person can’t be vaccinated, it’s important for the people around that person to be vaccinated. This can give the person some protection by reducing their exposure to disease.

Where to get advice about vaccines

It’s best to talk with your GP, child and family health nurse or paediatrician about vaccines. These people are health experts who know you and your family. They’ll listen to you, take the time to answer your questions, and give you the most up-to-date information about vaccines.

There are specialist immunisation services in most states and territories. These services are for children who’ve had adverse reactions to vaccines in the past or who are in high-risk groups, or for families who are concerned about vaccinating their children. You usually need a referral from your GP or specialist to go to one of these services.

Vaccines, vaccination and immunisation

You might hear the terms vaccine, vaccination and immunisation:

• A vaccine helps protects you from a disease. It’s a medicine.
• Vaccination means actually getting the vaccine, either by mouth or through injection.
• Immunisation means both getting the vaccine and being protected from the disease.

Most people use ‘vaccination’ and ‘immunisation’ to mean the same thing, although they’re not quite the same.