Children’s Health

Childhood Immunisation

What is immunisation?

Immunisation protects people against harmful infections before they come into contact with them in the community. Immunisation uses the body’s natural defence mechanism - the immune response - to build resistance to specific infections. Immunisation helps people stay healthy by preventing serious infections.
The diseases which can be prevented by routine childhood immunisation are included in the National Immunisation Program (NIP) Schedule.


How does immunisation work?

All forms of immunisation work in the same way.

When a person is vaccinated, their body produces an immune response in the same way their body would after exposure to a disease, but without the person suffering symptoms of the disease. When a person comes in contact with that disease in the future, their immune system will respond fast enough to prevent the person developing the disease.


What is in vaccines?

Vaccines contain either:

  • a very small dose of a live, but weakened form of a virus;
  • a very small dose of killed bacteria or virus or small parts of bacteria; or
  • a small dose of a modified toxin produced by bacteria.

Vaccines may also contain either a small amount of preservative or a small amount of an antibiotic to preserve the vaccine.
Some vaccines may also contain a small amount of an aluminium salt which helps produce a better immune response.


How safe are vaccines?

All vaccines currently available in Australia must pass stringent safety testing before being approved for use by the Therapeutic Goods Administration (TGA). This testing is required by law and is usually done over many years during the vaccine’s development.
Before vaccines are made available for use they are rigorously tested in thousands of people in progressively larger clinical trials. These trials are strictly monitored for safety. The approval process can take up to 10 years. As a result of such detailed testing, a number of vaccines that failed in these early tests have never been released.


How long do immunisations take to work?

In general, the normal immune response takes approximately two weeks to work. This means protection from an infection will not occur immediately after immunisation.

Most immunisations need to be given several times to build long lasting protection. For example, a child who has been given only one or two doses of diphtheria-tetanus-pertussis vaccine (DTPa) is only partially protected against diphtheria, whooping cough (pertussis) and tetanus, and may become sick if exposed to these diseases. However, some vaccines give protection after only one dose.


How long do immunisations last?

The protective effect of immunisations is not always for a lifetime. Some can last up to 30 years. Due to frequent changes to the influenza virus, annual influenza vaccination is needed to provide protection against the most recent virus.


Is everyone protected from disease by immunisation?

Even when all the doses of a vaccine have been given, not everyone is protected against the disease.
Measles, mumps, rubella, tetanus, polio and Hib vaccines protect more than 95% of children who have completed the course. One dose of meningococcal C vaccine at 12 months protects over 90% of children. Three doses of whooping cough (pertussis) vaccine protects about 85% of children who have been immunised, and will reduce the severity of the disease in the other 15% if they do catch whooping cough.
The protection levels provided by vaccines differ. For example, if 100 children are vaccinated with MMR, 5-10 of the fully immunised children might still catch measles, mumps or rubella (although the disease will often be milder in immunised children). However, if you do not immunise 100 children with MMR vaccine, and the children are exposed to measles, most of them will catch the disease with a high risk of complications like lung infection (pneumonia) or inflammation of the brain (encephalitis).
Booster doses are needed because immunity decreases over time.


Why do children get so many immunisations?

A number of immunisations are required in the first few years of a child’s life to protect the child against the most serious infections of childhood. The immune system in young children does not work as well as the immune system in older children and adults, because it is still immature. Therefore more doses of vaccine are needed.
In the first months of life, a baby is protected from most infectious diseases by antibodies from her or his mother, which are transferred to the baby during pregnancy. When these antibodies wear off, the baby is at risk of serious infections and so the first immunisations are given before these antibodies have gone.
Another reason why children get many immunisations is that new vaccines against serious infections continue to be developed. The number of injections is reduced by the use of combination vaccines, where several vaccines are combined into one shot.


Why should children be immunised?

There are two reasons for immunising every child in Australia:

  1. Immunisation is the safest and most effective way of giving protection against the disease. After immunisation, your child is far less likely to catch the disease if there are cases in the community. The benefit of protection against the disease far outweighs the very small risks of immunisation.
  2. If enough people in the community are immunised, the infection can no longer be spread from person to person and the disease dies out altogether. This is how smallpox was eliminated from the world and polio has disappeared from many countries.


Where can I find more information on childhood immunisation?

Parents and guardians are able to find information on routine childhood immunisation in the Understanding Childhood Immunisation booklet.
This is a detailed booklet which informs parents and guardians on why child/ren should be immunised against vaccine preventable diseases, common side effects of immunisation, how long immunisations last, vaccines their child/ren require at specific ages including the diseases they prevent and frequently asked questions. A handy quick guide to understanding childhood immunisation is also available.


Should parents be immunised?

Parents and other people (including grandparents, carers, etc) who come into contact with young children are commonly carriers of some childhood infections and should be vaccinated against these diseases. For example, several studies of infant pertussis (whooping cough) cases have indicated that family members, and parents in particular, were identified as the source of infection in more than 50% of cases. For more information on immunisations against childhood diseases, visit your local doctor or immunisation provider.


Are there any reasons to delay immunisation?

There are very few medical reasons to delay immunisation. If a child is sick with a high temperature (over 38ºC) then immunisation should be postponed until the child is recovering. A child who has a runny nose, but is not ill can be immunised, as can a child who is on antibiotics and obviously recovering from an illness.


What are the side-effects of immunisation?

Many children experience minor side effects following immunisation. Most side effects last a short time and the child recovers without any problems. Common side-effects of immunisation are redness, soreness and swelling at the site of an injection, mild fever and being grizzly or unsettled. You should give extra fluids to drink, not overdress the baby if hot and may consider using paracetamol to help ease the fever and soreness.
Serious reactions to immunisation are very rare, however if they do occur consult your doctor immediately. It is important to remember that vaccines are many times safer than the diseases they prevent.


What about natural immunity?

Natural immunity and vaccine-induced immunity are both natural responses of the body’s immune system. The body’s immune response in both circumstances is the same. In some cases, vaccine-induced immunity may diminish with time; natural immunity, acquired by catching the disease is usually life-long. The problem is that the wild or natural disease has a high risk of serious illness and occasionally death. Children or adults can be re-immunised (required with some vaccines but not all) if their immunity falls to a low level. It is important to remember that vaccines are many times safer than the diseases they prevent.


Can immunisation overload the immune system?

No. Children and adults come into contact with many antigens (substances that provoke a reaction from the immune system) each day, and the immune system responds to each antigen in specific ways to protect the body. Without a vaccine, a child can only become immune to a disease by being exposed to infection, with the risk of severe illness. If illness occurs after vaccination, it is usually insignificant.


Why is immunisation still necessary in this day and age?

Many diseases prevented by immunisation are spread directly from person to person, so good food, water and hygiene do not stop infection. Despite excellent hospital care, significant illness, disability and death can still be caused by diseases which can be prevented by immunisation.


Where can I find information about travel vaccinations?

Some health problems associated with international travel are vaccine preventable. Travellers should consult a travel medical centre, or their local doctor, at least 6 - 12 weeks before departure, for a check-up and to discuss required and recommended vaccinations for specific regions.
The websites below provide information about vaccinations and tips for staying healthy while overseas:


How do I get a copy of my child’s vaccination history?

Records are kept by the Australian Childhood Immunisation Register (ACIR) which is run by Medicare Australia.
ACIR was established in 1996 and is a national register administered by Medicare Australia that records details of vaccinations given to children under seven years of age who live in Australia. You can obtain a record of your child’s immunisation history from ACIR through the Medicare Australia website. You will need to register for online services at the following link, and then you will be able to request a history statement.
Department of Human Services Website
Alternatively, you can call ACIR on 1800 653 809 and request a statement be sent to you.
If your child was born before 1989 you will need to get in contact with the general practice, health centre or immunisation provider your child attended for the first two years of their life. They will be able to provide you with a copy of their medical records, including all immunisations they have had.