Dictionary of immunization terms
Active immunity: the production of antibodies against a specific disease by the immune system. Active immunity can be acquired can be acquired naturally or it can be induced. It is naturally acquired when a person is exposed to the live pathogen by contracting the disease and induced through vaccination. Active immunity is usually permanent and protection from the disease extends for the duration of the individual’s life.
Adjuvant: a substance which is mixed with an antigen to enhance the resulting immune response. An adjuvant is not antigenic by itself.
Adverse events: undesirable experiences occurring after immunization that may or may not be related to the vaccine
Antibody: a specialized immune protein (molecule) produced through the introduction of an antigen that possesses the capacity to bind to the specific antigen during an immune response. It can bind to a toxin, a virus or a bacterium and prevent them from attacking the body. The production of antibodies is a major function of the immune system.
Antigens: foreign substances (e.g. bacteria or viruses) in the body that are capable of causing disease. The presence of antigens in the body triggers an immune response, usually the production of antibodies.
Attenuated vaccine: a vaccine in which live pathogens are weakened to produce an immune response without causing the severe effects of the disease. For example, Sabin polio vaccine.
Auto-disable syringe: a specially modified disposable syringe with a fixed needle that is automatically disabled by plunger-blocking after it has been used once.
Bacteria: very tiny uni-cellular micro-organisms present throughout the environment. While not all bacteria are harmful, some are pathogenic and cause disease. Examples of bacterial disease include diphtheria, pertussis, tetanus, Haemophilus influenza and pneumococcus (pneumonia).
Booster shots: additional doses of a vaccine needed periodically to "boost" the immune system.
Bundling: a concept which requires that certain items must be ordered, distributed and used together. In the case of immunization, this concept applies to vaccines, diluent, syringes, needles and safety boxes. It does not necessarily apply that things are tied together physically.
Cellular vaccine: vaccine containing partial cellular material as opposed to complete cells.
Cold chain: a network of refrigerators, cold stores, freezers and cold boxes organized and maintained so that vaccines are kept at the right temperature to remain potent during vaccine orders and supplies, their transportation, storage and distribution from factory to the point of administration to the target population.
Cold room: a purpose made insulated enclosure fitted with refrigeration equipment which maintains a set temperature above 0°C.
Cold store: a facility where the cold room/freezer room or other refrigeration equipment is located, including a packaging area.
Combination vaccine: a vaccine against more than one pathogen, that is given in a single dose, such as the measles, mumps and rubella vaccine.
Communicable: capable of spreading disease. Also known as infectious.
Conjugate vaccine: a conjugate vaccine is created by covalently attaching a poor antigen to a carrier protein, thereby conferring the immunological attributes of the carrier on the attached antigen .
Contraindication: a condition or a disease which makes an individual temporarily or definitely unfit for a specific vaccination.
Control: reduction of a public health problem to a minor scale.
Diluent: a liquid used to reconstitute freeze-dried/lyophilized vaccine. Each such vaccine has its own diluent that cannot be used to reconstitute any other vaccine.
Drop-out rate: a comparison of the number of children or women who start receiving immunization and the number who do not receive later doses for full immunisation.
Efficacy: the extent to which a vaccine produces a specific outcome.
Elimination: reduction of disease incidence to under 1 per 1000 live births.
Endemic: the continual, low-level presence of disease in a community
Endemic disease: the constant presence of a disease or infectious agent within a given geographic area or population group.
Enzootic: the constant presence of a disease within a given animal population.
Epidemic: an outbreak of disease in human population.The occurrence, in a community or geographical region, of disease that is in excess normal occurrence.
Epidemiology: the study of how disease is distributed in a population and of the factors that influence or determine this distribution. Epidemiology helps to identify the causes and risk factors of a disease in a community.
Epizootic: an outbreak of disease in animal population.
Eradication: in which all transmission chains are broken, incidence falls globally to zero, and the etiologic agent is confined to WHO approved laboratories (like smallpox).
Etiology: the cause(s) of disease.
Expiry date: date after which the vaccine, diluent and other consumables (e.g. syringes, needles) should not be used for the purpose of immunization due to possible loss of potency (vaccines) or durability (consumables and other items).
Febrile: Feverish
Freezer room: a purpose made insulated enclosure fitted with refrigeration equipment which maintains a set temperature below 0°C.
Immunity: having sufficient biological defences for 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.
Immunization: the process of inducing or providing immunity by administering a vaccine, toxoid or antibody containing preparation.
Immune system: the complex system in the body that helps fight disease. Its primary function is to identify foreign substances in the body (bacteria, viruses, fungi or parasites) and develop a defence against them through the production of protein molecules called antibodies. The immune system differentiates between ‘invaders’ and the body’s own cells. When it fails to make this distinction, auto-immune diseases develop.
Immunosupression: suppression of the body’s immune system to fight infection and disease. This condition can be caused by diseases like HIV infection or cancer or by certain drugs (like those used in chemotherapy.
Inactive vaccine: a vaccine made from non-infectious, killed viruses and bacteria. These organisms have been killed through physical or chemical processes and cannot cause disease. They are differentiated from live/attenuated vaccines.
Incidence: the number of new cases of a disease during a specified period in a specified population. Incidence is usually expressed as cases per 1,000 or per 100,000 of the population per year.
Infectious: capable of spreading disease. Also known as communicable.
Infectious agents: organisms capable of spreading disease (e.g. bacteria or viruses).
Inventory: a physical count and assessment of the state and the functionality of the equipment and other materials used in cold chain.
Live vaccine: a vaccine that contains certain live cells of the disease in a weakened or attenuated form. Live vaccines are devoid of pathogenicity and when administered produce an immune response without causing the severe effects of the disease. Attenuated vaccines currently include measles, mumps, rubella, polio, yellow fever and varicella.
Logistics: a group of operations that include procurement, delivery of vaccines and consumables to the place of their use, management and maintenance of transport and cold chain equipment.
Maintenance: a series of technical activities (preventive and “curative”) that ensure smooth running of the equipment and transport facilities related to cold chain.
Outbreak: sudden appearance of a disease in a specific geographic area (e.g. neighbourhood or community) or population (e.g. adolescents).
Pandemic: referring to an epidemic disease of widespread prevalence around the globe.
Pathogens: organisms that cause disease in human beings and could include bacteria, viruses, parasites and fungi.
Polysaccharide vaccines: these vaccines that are made of extracted and purified forms of the bacterial outer polysaccharide coat. In other words, they consist of long chains of sugar molecules that resemble the surface of certain types of bacteria. Polysaccharide vaccines are available for pneumococcal disease, meningococcal disease and Haemophilus Influenzae type b.
Potency: a measure of strength.
Prevalence: a statistical definition of the number of cases of a disease existing in a particular population over a given time period.
Quarantine: the isolation of a person or animal who has a disease (or is suspected of having a disease) in order to prevent further spread of the disease.
Recombinant: of or resulting from new combinations of genetic material or cells.
Reconstitution of vaccine: to restore to former condition of freeze dried vaccines using specific diluent.
Seroconversion: development of antibodies in the blood of an individual who previously did not have detectable antibodies.
Serology: measurement of antibodies, and other immunological properties, in the blood serum.
Serosurvey: study measuring a person's risk of developing a particular disease.
Strain: a specific version of an organism. Many diseases, including HIV/AIDS and hepatitis, have multiple strains.
Supervision: supervision is a process to guide, support and assist service providers to carry out their duties and assigned tasks so as to achieve planned organizational goals. The process is based on observations, interviews, inspections, review of documentation that helps supervisors to assess the situation, and health workers to improve performance.
Titer: the detection of antibodies in blood through a laboratory test.
Toxicity: the extent, quality, or degree of being poisonous or harmful to the body.
Vaccination: to induce immunity by the presentation of whole or part of a pathogen to the body in order to stimulate an immune response. See immunization. Originally developed by Edward Jenner using material from cow pox lesions, the term is from the Latin "vacca" meaning "cow." See Immunization. "Vaccination" and "Immunization" are often used synonymously.
Vaccine: biological product prepared from killed or attenuated (weakened) virus or bacteria or their toxins, used for vaccinating people to induce specific immunity against an infectious disease.
Variolation: the old practice of inoculating someone with the virus of smallpox to produce immunity to the disease.
Vector: an insect that transports an infectious agent from an infected individual to a susceptible individual.
Virulence: the relative capacity of a pathogen to overcome body defenses.
Virus: a tiny organism that multiplies within cells and causes disease such as chickenpox, measles, mumps, rubella, pertussis and hepatitis. Viruses are not affected by antibiotics, the drugs used to kill bacteria.
Zoonosis: an infection or infectious disease transmissible under natural conditions from vertebrate animals to man.