The Australian Immunisation Handbook 10th Edition

Appendix 5: Glossary of technical terms

Page last updated: 01 August 2017

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a preparation added to a vaccine to improve the immune response to that vaccine

Adverse event following immunisation (AEFI)

an unwanted reaction following administration of a vaccine, which may or may not be caused by the vaccine; adverse events may be at the site of injection, or may be a general illness or a general allergic reaction


a sudden and severe allergic reaction, which results in a serious fall in blood pressure and/or respiratory obstruction and may cause unconsciousness and death if not treated immediately


the process of modifying a virus or bacteria to reduce its virulence (disease-inducing ability) while retaining its ability to induce a strong immune response (immunogenicity)


microorganisms that are smaller than a blood cell, but bigger than a virus; examples of bacterial infections are diphtheria, tetanus, pertussis, Hib and tuberculosis

Brachial neuritis

pain in the arm, causing persisting weakness of the limb on the side of vaccination


Chronically infected

formerly referred to as a ‘carrier’; a person who has an infection that, although not necessarily causing symptoms, may still be active and may spread to others; chronic infection may last for years; examples of infections that can result in chronically infected states are hepatitis B and typhoid


some bacterial vaccines (e.g. Hib, meningococcal and pneumococcal conjugate vaccines) are made from the chemical linking (conjugation) of a tiny amount of the ‘sugar’ (correctly known as the polysaccharide) that makes up the cell coat of the bacteria with a protein molecule, in order to improve the immune response to the vaccine


a reason why a vaccine or drug must not be given


a drug used to reduce inflammation and other immune responses


a vaccine that protects against diphtheria and tetanus. The acronym DT, using capital letters, signifies the child formulation of diphtheria and tetanus-containing vaccine, and denotes the substantially larger amounts of diphtheria toxoid in this formulation than in the adolescent/adult formulation.


reduced antigen content formulation of diphtheria-tetanus vaccine, which contains substantially lower concentrations of diphtheria toxoid, and approximately half the tetanus antigen content, than the child formulation (which is signified by using capital letters DT). This vaccine is most commonly administered to adolescents/adults.


a vaccine that protects against diphtheria, tetanus and pertussis (whooping cough). The DTP used in Australia and many other industrialised countries is DTPa, which contains an acellular pertussis component made of refined pertussis extracts instead of inactivated whole pertussis bacteria (DTPw). The acronym DTPa, using capital letters, signifies child formulations of diphtheria, tetanus and acellular pertussis-containing vaccines, and denotes the substantially larger amounts of diphtheria toxoid and pertussis antigens in these formulations than in the adolescent/adult formulations.


reduced antigen content formulation of diphtheria-tetanus-acellular pertussis vaccine, which contains substantially lower concentrations of diphtheria toxoid and pertussis antigens, and approximately half the tetanus antigen content, than the child formulations (which are signified by using all capital letters [DTPa]). This vaccine is most commonly administered to adolescents/adults.



the extent to which a vaccine produces a benefit in a defined population in uncontrolled or routine circumstances


the extent to which a vaccine produces a benefit in a defined population in controlled or ideal circumstances, for example, in a randomised controlled trial


inflammation of the brain


a general term to describe a variety of illnesses that affect the brain, including encephalitis


endemic infections are present all the time in a community


enzootic infections are present all the time in animals of a specific geographic area


epidemic infections are those that spread rapidly in a community; measles and influenza viruses are common causes of epidemics in Australia; small epidemics are often called outbreaks

Extensive limb swelling

swelling of the limb, with or without redness, which:

    • extends from the joint above to the joint below the injection site, or beyond a joint (above or below the injection site), or
    • results in the circumference of the limb being twice the normal size.


related to a fever, as in febrile illness and febrile convulsions



an inflammation of the liver; can be caused by viral infections

Hypotonic-hyporesponsive episode (shock, collapse)

the sudden onset of pallor or cyanosis, limpness (muscle hypotonia), and reduced responsiveness or unresponsiveness occurring after vaccination, where no other cause is evident, such as a vasovagal episode or anaphylaxis. The episode usually occurs 1 to 48 hours after vaccination and resolves spontaneously.


the process of inducing immunity to an infectious agent by administering a vaccine


the ability of the body to fight off certain infections; immunity can result from natural (‘wild’) infections or from vaccination


the ability (or the degree) to which a particular substance, in this context a vaccine, may provoke an immune response


a protein extract from blood, sometimes called ‘antibody’, that fights off infection; injection of immunoglobulins provides temporary immunity against certain infections

Incubation period

after a person is infected with bacteria or viruses, it often takes days or weeks for the infection to cause an obvious illness; the time between exposure to the infectious agent and development of the disease is called the incubation period


an infection occurs when bacteria or viruses invade the body; if the body cannot fight the infection, it may cause an illness

Intradermal (ID) injection

an injection into the surface layers of the skin; this is used for the administration of bacille Calmette-Guérin (BCG), the tuberculosis vaccine

Intramuscular (IM) injection

an injection into the muscle; vaccines are usually injected into a muscle of the upper outer thigh, or a muscle in the upper arm


when one portion of the bowel telescopes into the next portion of bowel, resulting in a blockage

Invasive disease

this term is often used when talking about pneumococcal or meningococcal disease. This term means that the bacteria (or germs) have been found in the blood, spinal fluid or another part of the body that would normally be sterile (or germ free).



yellow skin colour that may result from severe hepatitis



Pandemic influenza

a global epidemic that results when a new strain of influenza virus appears in the human population. It causes more severe disease in the population because there is little immunity to this new strain.


a medicine that helps reduce fever; it may be given to minimise fevers following vaccination


whooping cough, an illness caused by a bacterium, Bordetella pertussis


a group of complex carbohydrates (sugars), which make up the cell coating present in some bacteria

Polyvalent vaccine

a combination vaccine that protects against more than one disease; examples are DTPa and MMR


a virus that is a common cause of diarrhoea (and often vomiting as well) in young children. The diarrhoea can be severe in very young children, such that they may need intravenous fluids (i.e. through a vein in the arm) in hospital.


a viral illness, sometimes also known as German measles


a witnessed sudden loss of consciousness and generalised, tonic, clonic, tonic–clonic, or atonic motor manifestations.

Types of seizures include:

    • febrile seizures; with fever >38.5°C
    • afebrile seizures; without fever
    • syncopal seizures; a syncope/vasovagal episode followed by seizure(s).

Subcutaneous (SC) injection

an injection into the tissue between the skin and the underlying muscle


see vasovagal episode



platelet count <50 x 109/L

Transverse myelitis

a brief but intense attack of inflammation (swelling) in the spinal cord that damages myelin


the administration of a vaccine; if vaccination is successful, it results in immunity


a product often made from extracts of killed viruses or bacteria, or from live weakened strains of viruses or bacteria; the vaccine is capable of stimulating an immune response that protects against natural (‘wild’) infection


chickenpox, an infection caused by the varicella-zoster virus

Vasovagal episode (syncope, faint)

episode of pallor and unresponsiveness or reduced responsiveness or feeling light-headed AND occurring while vaccine is being administered or shortly after (usually within 5 minutes) AND bradycardia AND resolution of symptoms with a change in position (supine position or head between knees or limbs elevated)


a tiny living organism, smaller than a bacterium, that can cause infections; measles, rubella, mumps, polio, influenza and hepatitis B are examples of viruses



an abbreviation for herpes zoster infection (also known as shingles); a painful rash and illness, caused by the varicella-zoster (chickenpox) virus