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Immunisation

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Immunisation
Summary
  • Immunisation is a simple, safe and effective way of protecting children and adults from diseases such as diphtheria, tetanus, whooping cough, polio and measles.
  • Immunisation involves a vaccine being injected or swallowed.
  • The body then recognises the vaccine as a disease and develops antibodies (proteins that fight infection) against it.
Description

Immunisation involves the injection or oral dose of a vaccine which produces an immune response to a particular disease without causing the person to contract the disease. Immunisation is a simple, safe and effective way of protecting children and adults from diseases such as diphtheria, tetanus, whooping cough, polio, measles, mumps, rubella, chickenpox, Haemophilus influenzae b (Hib) and hepatitis B.1

Vaccination is the term used to describe the actual injection or oral dose of vaccine. Immunisation is the term used to describe both the process of receiving the vaccine and becoming immune to the disease as a result. Vaccination and Immunisation are terms often used interchangeably, however the meanings are not exactly the same because immunity follows vaccination in most, but not all cases.

All forms of Immunisation work the same way. Immunisation involves a vaccine being injected or swallowed. The body then recognises the vaccine as a disease and develops antibodies (proteins that fight infection) against it. Because the vaccine is a weak or dead version of the disease, the person will not contract the illness. Next time the immunised person comes in contact with the disease, the antibodies will recognise and fight it. It is important to be aware, however, that in rare cases vaccination is ineffective and does not result in a person being immunised against the particular disease.

WHAT IS A VACCINE?

Some vaccines contain a very small dose of a live, non-harmful form of a virus. Some vaccines contain a very small dose of killed bacteria or small parts of bacteria and other vaccines contain a small dose of modified toxin produced by bacteria.

HOW LONG DOES IT TAKE TO WORK?

The normal immune response takes several weeks to work. This means protection from an infection will not occur immediately after immunisation. Some Immunisations need to be given several times to build long lasting protection. This is called a booster.

HOW EFFECTIVE ARE IMMUNISATIONS?

Some Immunisations give lifelong protection after one dose, while other types will need booster shots. There are a small number of people who will not develop antibodies even after receiving all doses of a vaccine. Generally 85-95% of people will be adequately immunised. The remainder can still be protected from the diseases if other people around them are immunised. Remember that while some of these diseases (such as poliomyelitis) have been eradicated, the organisms that cause them are still in the environment. If Immunisation levels drop, the incidence of disease will increase again.

SIDE EFFECTS

Side effects are usually very mild. Often the injected limb will be sore, with a small, red lump at the site. The tetanus vaccination can be particularly painful. Use a cold pack on the site if it becomes troublesome. Sometimes there may also be a mild fever, which can be relieved with paracetamol. Some people may develop a slight rash a couple of weeks later, which is an indication an immune response has occurred. Serious reactions such as febrile convulsions, vomiting or encephalitis are extremely rare. See the Immunisation - Side Effects topic for further information.

  • Management

    Immunisations may not be recommended for:

    • Pregnant women and those planning to become pregnant within one month. When a vaccine is to be given during pregnancy, it should be delayed until the second or third trimester if possible. Pregnant women should avoid exposure to people with infectious illnesses.2 - People with severely weakened immune systems.3 This may be due to some types of cancer, chemotherapy treatment, leukaemia, high doses of steroids, symptomatic HIV/AIDS or transplant surgery.
    • People who are allergic to egg proteins, yeast or neomycin, as some vaccines contain these substances.4
    • People with a high-grade fever (higher than 38 degrees Celsius/99 degrees Fahrenheit).5
    • Children with moderate to severe diarrhoea, middle ear infection or vomiting.6


    NOTE: In some of the above cases, immunisation may still be recommended, as the disease itself may be more harmful than the vaccine. Your Doctor will help you establish the risks and benefits for your condition.

    Immunisations are generally considered safe for:

    • People who have mild reactions to previous Immunisations.
    • People with neurological disorders such as cerebral palsy, Down syndrome, epilepsy or convulsions.7
    • People who have already had one or more of the infectious illnesses covered by the vaccine.8
    • Premature babies.9
    • Family history of sudden infant death syndrome (SIDS).10
    • People with asthma, eczema, hay fever or simple allergies.
    • People with a runny nose, mild cold, low-grade fever or other mild illness.11
    • People on antibiotics or low doses of steroids.12
    • Babies being breast-fed or bottle-fed.
    • Children over the age recommended in the standard Immunisation schedule.


  • Notes

    References

    1. CDC. Prevention of varicella: Recommendations of the advisory committee on immunisation practices (ACIP). Morbidity and Mortality Weekly Report 45(RR-11):1-36, 1996.
    2. Immunisation of preterm infants. Red Book: Report of the Committee on Infectious Diseases (25th ed) 2000.
    3. Common myths about Immunisations. American Academy of paediatrics 2000. At URL http://www.medem.com
    4. Beers M et al (eds). The Merck manual of diagnosis and therapy (17th ed). Merck Research laboratories; 1999
    5. Beers M et al (eds). The Merck manual of diagnosis and therapy (17th ed). Merck Research laboratories; 1999
    6. Contraindications for childhood immunisation. CDC 2001. At URL http://www.cdc.gov/nip/recs/contraindications.pdf
    7. Contraindications for childhood immunisation. CDC 2001. At URL http://www.cdc.gov/nip/recs/contraindications.pdf
    8. Beers M et al (eds). The Merck manual of diagnosis and therapy (17th ed). Merck Research laboratories; 1999
    9. Immunisation of preterm infants. Red Book: Report of the Committee on Infectious Diseases (25th ed) 2000.
    10. Contraindications for childhood immunisation. CDC 2001. At URL http://www.cdc.gov/nip/recs/contraindications.pdf
    11. Contraindications for childhood immunisation. CDC 2001. At URL http://www.cdc.gov/nip/recs/contraindications.pdf
    12. Contraindications for childhood immunisation. CDC 2001. At URL http://www.cdc.gov/nip/recs/contraindications.pdf
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