Immunisation Glossary of Terms

A

Acquired Immune Deficiency Syndrome (AIDS)

A medical condition where the immune system cannot function properly and protect the body from disease. As a result, the body cannot defend itself against infections (like pneumonia). AIDS is caused by the Human Immunodeficiency Virus (HIV). The virus is spread through direct contact with the blood and body fluids of an infected individual. High-risk activities include unprotected sexual intercourse and intravenous drug use (sharing needles). There is no cure for AIDS. However, research efforts are on-going to develop a vaccine.

Adjuvant

Adjuvant is a compound used to increase antigenicity and to prolong the stimulatory effect of vaccines particularly of those containing inactivated microorganisms or their products (eg diphtheria and tetanus toxoids).

AEFI

Adverse effects following immunisation.

Allergy

A condition in which the body has an exaggerated response to a substance (eg food or drug). Also known as hypersensitivity antibodies. Proteins produced by the body to neutralise or destroy toxins and disease-carrying organisms.

Antigen

An antigen is defined as anything that provokes an immune response, which is specific to that material. It can be a single molecule or a more complex structure such as a bacteria or virus.

Antitoxin

Antitoxin is a solution of antibodies derived from the serum of animals immunised with specific antigens (eg diphtheria antitoxin) used to achieve passive immunity or for treatment.

Attenuated

Weakened pathogens (organisms that produce disease eg a virus) are attenuated to make them safe when used in a vaccine.

Autism

A lifelong disability that affects the way a person communicated and relates to other people. It usually involves poor social interaction, poor social communication and limited imagination.

B

Bacteraemia

Bacteraemia occurs when bacteria get into the bloodstream. Bloodstream infection is also sometimes called septicaemia, which implies greater severity/clinical significance. A wide variety of bacteria can cause bacteraemias, the two most common being Staphylococcus aureus and Escherichia coli.

Bacterium/Bacteria

Bacterium/Bacteria are single-cell micro-organisms, some of which cause disease. Others are essential for our bodies to work properly.

BCG

Bacille Calmette-Guérin vaccine

Booster

An extra dose of vaccine that builds up immunity to the disease the vaccine protects against.

C

CDC
Centre for disease control

Cellulitis
Bacterial skin infection. Resulting in a sore, hot, painful area of skin. May lead to Septicaemia a form of blood poisoning.

Conjugate vaccine
Conjugate vaccines contain carrier proteins which, when combined with antigens, enhance the type and magnitude of the immune response. Examples include Haemophilus influenza B, Meningococcal conjugate and Pneumococcal conjugate vaccines.

D

Diabetes
A chronic health condition where the body is unable to produce insulin and properly breakdown sugar (glucose) in the blood. Symptoms include hunger, thirst, excessive urination, dehydration and weight loss. The treatment of diabetes requires daily insulin injections, proper nutrition and regular exercise. Complications can include heart disease, stroke, neuropathy, poor circulation leading to loss of limbs, hearing impairment, vision problems and death.

DoHC
Department of Health and Children

E

Encephalitis
Inflammation of the tissues of the brain which can cause lasting brain damage.

Encephalopathy
Any disease of the brain.

Endemic
A disease restricted to a place, region or population

Epidemic
An outbreak of a disease that spreads within a community. A pandemic is an epidemic over a vast area - it usually refers to an outbreak that affects several countries.

Epiglotitis
Inflammation or swelling of the epiglottis that can cause a blockage of the airway, which can be fatal.

F

Febrile convulsions
seizures, that may be caused by a rise in body temperature.

H

Hepatitis A
A minor viral disease that usually does not persist in the blood; transmitted through ingestion of contaminated food or water.

Herd Immunity
Vaccination protects the individual immunised who is less likely to be a source of infection to others. This reduces the risk of unimmunised individuals being exposed to infection. Thus, individuals who have not been immunised, or those who cannot be immunised, get some benefit from the immunisation programme. This concept can also be called population immunity.

Hexavalent Vaccine
is a combined vaccine that protects against six different diseases. An example is the 6 in 1 vaccine that protects against Diphtheria, Tetanus, Pertussis (Whooping Cough), Polio, Haemophilus Influenzae b, Hepatitis B.

Abbreviations

Hib
Haemophilus influenza type b

HIV
Human Immunodeficiency Virus

HNIG
Human Normal Immunoglobulin

HPSC
Health Protection Surveillance Centre

HPV
Human Papillomavirus

HIQA
Health Information and Quality Authority

HSE
Health Service Executive

I

Idiopathic
is a term used to describe a disease or disorder that has no known cause.

Immunisation
donates the process of inducing or providing immunity artificially. This may be either active or passive.

Immune system
The body's system for fighting infectious disease.

Immunity
Protection against a disease. There are two types of immunity, passive and active. Immunity is indicated by the presence of antibodies in the blood and can usually be determined with a laboratory test. See active and passive immunity.

Immunoglobulin
Human immunoglobulin is that fraction of blood plasma that contains antibodies, notably those against infectious agents.

Preparations of immunoglobulin belong to 2 main categories:

Human Normal Immunoglobulin (HNIG)
Human Specific Immunoglobulin / Hyperimmune Globulin

Inactivated vaccine
These vaccines are manufactured either from the killed germ, or from the toxin, or using parts of the germ either as component vaccines or as conjugate vaccines.

Abbreviations

IM
Intramuscular

IMB
Irish Medicines Board

IPD
Invasive Pneumococcal Disease

IPV
Inactivated Polio Vaccine

J

Jaundice
Yellowing of the eyes. This condition is often a symptom of hepatitis infection.

K

Killed vaccine
These vaccines are made from the killed germ or virus which causes the disease. Killed vaccines in the childhood immunisation schedule include whole cell pertussis, inactivated polio. Whole cell typhoid is also a killed vaccine.

L

Live attenuated vaccine
This is a vaccine made from the live virus which has been altered to make it less harmful. The live vaccines in the childhood immunisation schedule are oral polio, MMR and BCG. Other live vaccines include yellow fever and one form of typhoid vaccine.

Low grade fever
A slightly raised body temperature

Lymph nodes
Small glands that store cells that act as the body's first line of defence, fighting infection and other diseases, including cancer.

M

Meningitis
Inflammation or swelling of the lining of the brain

Myalgia
General muscle aches and pains.

Abbreviations

MenB
Meningococcal B

MenC
Meningococcal C

MenACWY
Meningococcal A, C, W, Y

MMR
Measles, Mumps, Rubella

N

Abbreviations

NIAC
National Immunisation Advisory Committee

NIO
National Immunisation Office

O

Oral vaccine
A vaccine taken by swallowing it.

Osteomyelitis
Inflammation of the bone. Resulting in fever, painful limbs . May lead to long-term bone infection.

Abbreviations

OPV
Oral Polio Vaccine

P

Pandemic
An epidemic occurring over a very large area.

Pathogen
is an organism that produces disease eg a bacteria or virus

Pentavalent Vaccine
is a combined vaccine that protects against 5 diseases and example is the 5 in 1 vaccine it protects against Diphtheria, Tetanus, Whooping Cough, Polio and Hib.

Pericarditis
Inflammation of the membrane that surrounds the heart. Resulting in chest pain, breathing difficulties. Can be fatal.

Pharmacoeconomics
is the branch of health economics that focuses on the cost and benefits of drug treatments, including vaccines. It includes a comprehensive analysis of all alternative courses of action in terms of cost and human gain.

Pneumonia
Inflammation of the lungs due to infection

Abbreviations

PPV
Pneumococcal Polysaccharide Vaccine

PCCC
Primary, Community and Continuing Care

PCV
Pneumococcal Conjugate Vaccine

PPD
Purified Protein Derivative

R

Rotavirus

Rotavirus is a viral infection which causes diarrhoea and vomiting in babies and young children. It is very infectious. It is the most common cause of gastroenteritis in children in Ireland under the age of 5 years. It is most common in the Spring and Winter.

S

Septicaemia
A form of blood poisoning

Septic arthritis
(serious infection in a joint) Resulting in fever, painful, red, hot and swollen joints. May lead to permanent damage to joints.

Splenectomy
an operation to remove the spleen

Subacute sclerosing panencephalitis (SSPE)
A rare degenerative neurological condition which progressively destroys nerve cells in the brain leading to mental deterioration and death. It occurs some years after measles disease (average interval around 8 years). Those children affected by the disease at a young age are at particular risk.

Abbreviations

SC
Subcutaneous

SPC
Summary of Product Characteristics

SSPE
Subacute Sclerosing Panencephalitis

T

Tetravalent Vaccine
is a combined vaccine that protects against 4 diseases an example would be the 4 in 1 vaccine that protects against Diphtheria, Pertussis, Polio, Tetanus.

Thiomersal
Thiomersal is a mercury-containing compound that has been used since the 1930s to prevent contamination in some vaccines. Thiomersal is NOT the same as methyl mercury, which can accumulate in the body and become toxic. A European review of the available evidence concluded that there is no evidence of harm from thiomersal in vaccines other than hypersensitivity reactions. The WHO has concluded that there is no evidence of mercury toxicity in infants, children, or adults exposed to thiomersal in vaccines.

Thrombocytopenia
is a disorder in which there are not enough platelets. This can be due to

Low production of platelets in the bone marrow
Increased breakdown of platelets in the bloodstream (called intravascular)
Increased breakdown of platelets in the spleen or liver (called extravascular)

Toxin
A poison produced by bacteria.

Toxoid containing vaccine
These vaccines are made from the toxin (poison) which has been made harmless. Diphtheria and tetanus are toxoid vaccines.

Abbreviations

Td
Tetanus toxoid, low dose diphtheria toxoid vaccine

Tdap
Tetanus, low dose diphtheria and low dose pertussis vaccine

TB
Tuberculosis

V

Vaccine
Vaccines are manufactured in different ways using part of the germ or virus which causes the disease. Except very rarely (oral polio vaccine only) they cannot cause the disease for which they give protection.

Virus
An organism that needs to live inside a cell to grow and reproduce. Viruses cause many types of disease, including the common cold.

Vaccination
is a term used to refer to the administration of any vaccine or toxoid.

This page was updated on 14 August 2019