Technical term Explanation
acellular vaccine

A vaccine that contains cellular material but does not contain complete cells


A substance that is added to a vaccine during production to improve the immune response to that vaccine


A person aged 10–19 years


A person aged over 19 years

adverse event following immunisation

An unwanted medical reaction after administration of a vaccine, which may or may not be related to the vaccine. Adverse events may be at the site of injection, a general illness or a general allergic reaction.


An immune response to a foreign substance that is harmless in most people. The foreign substance could be a food, medicine or vaccine component


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


A foreign substance that induces an immune response, usually the production of antibodies


A condition in which a person’s spleen has been removed (anatomical asplenia) or does not function (functional asplenia)


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

Australian Immunisation Register

A database that holds records of vaccinations given to people of all ages who are registered with Medicare in Australia. Immunisation providers need to enter details of the vaccinations they give on the AIR. The AIR is an expansion of the previous Australian Childhood Immunisation Register (ACIR), which recorded vaccinations given to children under 7 years of age


Microorganisms that are smaller than a blood cell, but bigger than a virus; examples of diseases caused by bacteria are diphtheria, tetanus, pertussis, Haemophilus influenzae type b (Hib) and tuberculosis

brachial neuritis

Pain in the arm that a vaccine was given in, causing persisting weakness of the arm

breakthrough infection

Development of a disease despite previous vaccination against the infectious agent


’Carriage’ means the presence of meningococcal bacteria in the upper respiratory tract without any signs or symptoms of infection.

catch-up vaccination

The process of planning and scheduling vaccines for people who have missed 1 or more doses of scheduled vaccines


A person aged 12 months to <10 years

chronic infection

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 diseases that can cause chronic infection are hepatitis B and typhoid. People with chronic infections used to be referred to as ‘carriers’

cold chain

The system of transporting and storing vaccines within the temperature range of +2°C to +8°C from the place of manufacture to the point of administration. This is essential for maintaining vaccine potency and vaccine effectiveness

combination vaccine

2 or more vaccines given in a single dose that protects against more than 1 disease. Examples are DTPa (diphtheria-tetanus-acellular pertussis) and MMR (measles-mumps-rubella) vaccines

conjugate vaccine

A type of bacterial vaccine that is made by chemically linking (conjugating) a protein molecule with a tiny amount of the polysaccharide that makes up the cell coating of the bacterium. This improves the immune response to the vaccine. Examples are Haemophilus influenzae type b (Hib), meningococcal and pneumococcal conjugate vaccines


A medical condition or risk factor in a recipient/person that makes receiving a specific vaccine potentially harmful


A medicine used to reduce inflammation and other immune responses


A measure of how well a vaccine works in a defined population in ‘uncontrolled’ or routine circumstances — for example, in a vaccination program


A measure of how well a vaccine works 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


Ongoing, low-level presence of a disease in a community


Occurrence of a disease at a steady rate in animals in a specific geographic area


The spread of an infection in a community at a faster rate than is normally expected. 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, that:

  • extends from the joint above the injection site 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 — for example, febrile illness and febrile convulsions

Guillain–Barré syndrome

An autoimmune condition that causes muscle weakness, numbness or paralysis

HALO principle

Health, Age, Lifestyle, Occupation. This helps assess which vaccines adults need based on their risk factors

herd immunity

A situation in which a large proportion of the population is immune to a disease through previous vaccination or illness. As a result, it is highly unlikely that the disease will spread from person to person. Non-immune people are indirectly protected from the disease

humoral immunity

The aspect of immunity that involves antibodies and other proteins to fight infection

hypotonic-hyporesponsive episode (shock, collapse)

The sudden onset of:

  • pallor or cyanosis
  • limpness (muscle hypotonia)
  • reduced responsiveness or unresponsiveness

This may occur after vaccination when no other cause is evident, such as a vasovagal episode or anaphylaxis. The episode usually occurs 1–48 hours after vaccination and gets better on its own without treatment


The process of inducing immunity to an infectious agent by giving a vaccine

immunisation provider

Any person who provides vaccines to people. Immunisation providers can work in many settings, including:

  • general practice
  • local council clinics
  • community centres
  • pharmacies
  • Aboriginal Community Controlled Health Services
  • school-based immunisation programs
  • travel medicine clinics
  • hospitals
  • staff occupational health clinics
  • aged care facilities

The ability of the body to fight off an infection. Immunity can result from natural infections or from vaccination


Having an immune system that is weakened and unable to protect the body from disease. It can be caused by disease (such as HIV infection or cancer) or some medicines (such as those used in chemotherapy)


The ability of a particular substance, such as a vaccine, to provoke an immune response, or the degree of response it provokes


A protein extracted from blood, sometimes called an antibody, that fights infection. An injection of immunoglobulins provides temporary immunity against certain infections (also known as passive immunisation)


See immunocompromised


immunosuppressive therapy

Medicines used to treat certain conditions, but that also weaken the immune system. Examples are chemotherapy, radiation therapy and oral corticosteroids

incubation period

The time between exposure to an infectious agent and development of disease. It can take days or weeks for an infection with a virus or bacterium to cause an obvious illness


A person aged under 12 months


When bacteria or viruses invade the body. If the body cannot fight the infection, it may cause disease

intradermal injection

An injection into the surface layers of the skin. This type of injection is used to administer BCG (bacille Calmette–Guérin) vaccine to prevent tuberculosis

intramuscular injection

An injection into the muscle. Vaccines are usually injected into a muscle in the upper outer thigh or upper arm


A condition in which one portion of the bowel telescopes into the next portion of the bowel, resulting in a blockage

invasive disease

When bacteria are found in the blood, spinal fluid or another part of the body that would normally be sterile. This term is often used in relation to pneumococcal or meningococcal disease


Institut Pasteur du Cambodge


Yellow skin colour that may result from severe hepatitis

live vaccine

A vaccine containing live viruses or bacteria that are weakened (attenuated) to produce an immune response in the recipient without causing the serious effects of the disease

minimum interval

The shortest amount of time required between 2 doses of a vaccine to provide an adequate immune response to the 2nd dose. If the interval between the doses is shorter than the minimum interval, the vaccine may not be effective

National Immunisation Program

A program in Australia that funds free vaccines for eligible people to increase immunisation rates and help reduce vaccine-preventable diseases

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 few people have immunity to the new strain

passive immunity

Direct transfer or administration of antibodies to a non-immune person. Examples are transfer of maternal antibodies to an infant before birth and administration of immunoglobulins

polysaccharide vaccine

A type of bacterial vaccine that contains a group of complex carbohydrates (sugars) that make up the cell coating of the bacterium

post-exposure prophylaxis

Providing immunoglobulin (or sometimes vaccine) to a person who has been exposed to an infectious agent, in an effort to prevent them developing the disease

pre-exposure prophylaxis

Providing a medicine or vaccine to a person who may be at risk of a disease but who has yet not been exposed to the infectious agent. This will help to prevent them developing the disease if they are later exposed to it


A medical condition or risk factor in a person that may increase the risk of an adverse reaction to a vaccine, or could compromise the ability of the vaccine to induce immunity. The benefits and risks should be assessed when considering vaccination for a person with a precaution. See also contraindication

preterm infant

An infant born prematurely. Preterm infants are those born at <37 weeks gestation. Extremely preterm infants are those born at <28 weeks gestation


The ability of a vaccine to cause adverse reactions, or the severity of adverse reactions it causes

school-based program

A method of delivering vaccines to children and adolescents. In Australia, it is mostly used for vaccines that are given to adolescents in specific school grades


A 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, with fainting (syncope, vasovagal episode) followed by seizure(s)
serological testing

Testing for specific antibodies, or other markers of infection or immunity, usually from a blood sample

subcutaneous injection

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


See vasovagal episode


Abnormally low levels of platelets in the blood (<50 × 109/L)


updated Thai Red Cross


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. A vaccine can stimulate an immune response that protects against natural infection

vasovagal episode (syncope, fainting)

An episode that involves all of the following:

  • pallor and unresponsiveness, reduced responsiveness or feeling light-headed
  • bradycardia
  • resolution of symptoms with a change in position (supine position, head between knees or limbs elevated)

A vasovagal episode may occur while vaccine is being administered or shortly after (usually within 5 minutes)


A tiny living organism, smaller than a bacterium, that can cause infections. Examples of diseases caused by viruses are measles, rubella, mumps, polio, influenza and hepatitis B

Page history

Last updated: 
12 June 2017
Last reviewed: 
6 February 2019