Immunisation - common misconceptions

Australian research shows that parents are concerned about vaccine safety and effectiveness. Since few people have had any direct experience of childhood diseases, they tend to underestimate their effects and complications.

Vaccines and the immune system
The immune system is a collection of specialised cells and chemicals that fight infection. Each time an infectious agent is overcome, the immune system ‘remembers’ how it was defeated. If the immune system comes in contact with that particular infectious agent again, it can destroy it quickly - often before the person even notices any symptoms of illness. Vaccines work by introducing dead or weakened versions of disease-causing organisms to the immune system. If and when the immune system encounters the ‘real’ disease-causing organisms, quick recognition allows a rapid and effective immune response.

The infant immune system
The human immune system is developed from birth. An infant is exposed to many germs as part of the normal birthing process, including from the vaginal canal, faeces and breast milk. Their immune system is immediately ready to meet these challenges. However, the immune system in an infant is inexperienced and needs to become active to protect against a range of bacteria and viruses from the start.

An infant will receive some natural protection against diseases transferred from the placenta but the level of protection depends on the mother’s exposure to the diseases either by illness or vaccination. Breast milk is also valuable for protection but the protection is mainly for germs that infect the gut. The protection received from the placenta and breast milk only lasts for a few months.

Vaccines don’t reduce immunity
There are concerns that combining two or three vaccines into one injection may put a baby’s immune system under considerable strain. It has been suggested that vaccines should be separated and given at six-monthly or yearly intervals. However, this would leave children vulnerable to catching diseases in the meantime. Contrary to popular belief, vaccines don’t reduce a child’s immunity.

Vaccine preparations contain dead or weakened organisms that don’t cause infection, so an ‘all-out’ immune response is not needed. In addition, the immune system is designed to handle multiple responses, because germs don’t attack the body one at a time. Each vaccine is made differently and carefully researched to be recommended at an age for earliest protection and best effect.

Vaccine safety
Vaccines are safe and efficient ways to prevent the spread of many communicable diseases. Every vaccine used in Australia was thoroughly tested for safety and effectiveness, passed for use by the Therapeutic Goods Administration, and subject to ongoing monitoring and evaluation. However, vaccines are like any other medication - they may trigger side effects. This is why parents are generally advised to remain at the clinic for at least 15 minutes after their children are immunised. In the majority of cases, side effects are mild.

Autism, sudden infant death syndrome (SIDS) and diabetes
Some researchers have proposed that vaccinations can cause certain disorders, such as autism and diabetes, or else contribute to the risk of sudden infant death syndrome (SIDS). These theories have since been investigated and dismissed. Immunisation reactions are generally mild and resolve by themselves without needing medical treatment. Reactions may include fever and soreness at the injection site. Serious immunisation reactions are exceptionally rare.

The risk of childhood diseases
Parents who are fearful of autism or SIDS may choose not to have their children vaccinated. If vaccination levels fall too low, disease epidemics can flourish. Since most people have little first hand experience of childhood infectious disease, they underestimate the effects and complications. Childhood diseases such as measles and whooping cough are serious and potentially fatal.

The risk of complications from disease is much higher than the risks of immunisation. For example, some parents are worried that the Measles Mumps Rubella vaccine can cause brain inflammation (encephalitis). The risk is around one in 1,000,000. However, one in every 2,000 children who catch measles will experience encephalitis. Of these, 10 per cent will die and 40 per cent will be permanently brain damaged.

The effectiveness of vaccination
Some parents don’t have their children immunised because they believe that vaccines don’t work. It is true that some people still catch a disease even though they have been vaccinated against it. No vaccine can offer complete immunity against disease for everyone, but effectiveness rates are high:

• Diphtheria - out of 100 vaccinated people, 84 will be completely immune.
• Haemophilus influenzae type b (Hib) - out of 100 vaccinated people, 95 will be completely immune.
• Measles - out of 100 vaccinated people, 95 will be completely immune.
• Pertussis - out of 100 vaccinated people, more than 80 will be completely immune.
• Polio - out of 100 vaccinated people, 95 will be completely immune.
• Meningococcal C - out of 100 vaccinated people, 96 to 98 will be completely immune.

• Your doctor
• Your local council immunisation service
• Immunisation Program - Department of Health Victoria, Tel. 1300 882 008
• The Maternal and Child Health Line is available 24 hours a day Tel. 132 229.
• National Immunisation Infoline Tel. 1800 671 811

• Australian research shows that parents are concerned about vaccine safety and effectiveness.
• Immunisation reactions are generally mild and resolve by themselves without needing medical treatment.
• The risk of complications from childhood diseases is much higher than the risks of immunisation.

This page has been produced in consultation with and approved by:


(Logo links to further information)