Skip Navigation

United States Department of Health & Human Services
line

Print Print    Download Reader PDF

 

DEFINITIONS OF TERMS RELATED TO IMMUNIZATION

adjuvant: A substance that is used in a vaccine to improve the immune response so that less vaccine is needed to produce a non-specific stimulator of the immune response.

adult immunizations: Vaccinations that are given to people over 18 years of age (i.e. booster tetanus shots, annual influenza shots, and pneumococcal or pneumonia vaccine).

adverse event: Any undesirable side effect that may result from a vaccination.

agammaglobulinemia: A rare disease in which the body is not able to produce immune antibodies due to a lack of gamma globulin (a type of immunoglobulin) in the blood.

anaphylaxis: An immediate and severe allergic response; a shock reaction to a substance. This can result in sudden severe breathing difficulty, severe drop in blood pressure, and/or loss of consciousness. Anaphylactic shock can kill if not treated promptly. Common causes of anaphylaxis include: bee stings in people that are allergic to bees, ingestion of certain foods by people that are allergic to those foods, and drug reactions.

antimicrobial agents: A general term for the drugs, chemicals, or other substances that kill microbes (tiny organisms that cause disease). Among the antimicrobial agents in use today are: antibacterial drugs (kill bacteria); antiviral agents (kill viruses); antifungal agents (kill fungi); and antiparisitic drugs (kill parasites).

attenuated: To be weakened. An attenuated vaccine is one that has been weakened by chemicals, or other processes so that it will produce an adequate immune response without causing the serious effects of an infection.

bacteria: (Plural for bacterium). Tiny microorganisms that reproduce by cell division and usually have a cell wall. Bacteria can be shaped like a sphere, rod, or spiral and can be found in virtually any environment.

booster: Administration of an additional vaccination to help increase or speed the immune response to a previous vaccination.

childhood immunizations: A series of immunizations that are given to prevent diseases that pose a threat to children. The immunizations in the United States currently include: Hepatitis B, Diphtheria, Tetanus, Acellular Pertussis, Haemophilus Influenzae type b, Inactivated Polio, Pneumococcal Conjugate, Measles, Mumps, Rubella, Varicella, and Hepatitis A.

combination vaccine: A combination of two or more vaccines (i.e. the diphtheria/tetanus/pertussis vaccine). Like the individual vaccines, combination vaccines are developed through scientific research. They are also tested through clinical trials for appropriateness, safety, and effectiveness before they are licensed and released for use by the public.

community immunity: A concept of protecting a community against certain diseases by having a high percentage of the communityís population immunized. (Sometimes referred to as "herd" immunity). Even if a few members of the community are unable to be immunized, the entire community will be indirectly protected because the disease has little opportunity for an outbreak. However, with a low percentage of population immunity, the disease would have great opportunity for an outbreak.

Examples of the key role of community immunity include being vaccinated with Hepatitis B, Diphtheria, Acellular Pertussis, Haemophilus Influenzae type b, Inactivated Polio, Pneumococcal Conjugate, Measles, Mumps, Rubella, Varicella, and Hepatitis A because these are diseases that can spread through person-to-person transmission. Tetanus, on the other hand, cannot be spread through person-to-person transmission. It is transmitted through skin wounds. For example, if a person steps on a nail or sustains some kind of penetrating injury from something that has been contaminated with Tetanus spores, there is significant risk for a life-threatening Tetanus infection. The level of community immunity would have no impact on this risk.

conjugate vaccines: A vaccine in which a polysaccharide antigen is chemically joined with a protein molecule to improve the immunogenicity of the polysaccharide.

conjunctivitis: Inflammation of the eyelid. Sometimes this condition occurs independently, but it can also occur with other illnesses (i.e. measles).

contraindication:Any condition (especially of disease), which renders some particular line of treatment improper or undesirable.

disease: Sickness; illness; an interruption, or disturbance of the bodily functions or organs, which causes or threatens pain and weakness.

encephalitis: Inflammation of the brain and central nervous system.

epidemic: An outbreak of disease that spreads within a specific region and/or country.

Hib disease: Disease caused by Haemophilus Influenzae type b. Until recently, this disease was the most common cause of deadly bacterial meningitis in children. It can also cause infection of the bloodstream, pneumonia, epiglottis, and otitis media, among other conditions.

hypogammaglobulinemia: Abnormally low levels of all classes of immunoglobulins.

immune: A state of being protected against infectious diseases by either specific or non-specific mechanisms (i.e., immunization, previous natural infection, inoculation, or transfer of protective antibodies). For certain diseases, immune mothers may temporarily transfer protective antibodies to their newborns through the placenta. Protection can result from this placental transfer for up to 4-6 months.

immune system: The bodyís very complex system (made of many organs and cells), which defends the body against infection, disease, and foreign substances.

immunity: The condition of being immune or protected against infection, disease, and foreign substances.

immunization: A process or procedure that increases an organismís reaction to antigens, thereby, improving its ability to resist or overcome infection.

immunoglobulins: A specific protein substance, produced by plasma cells to help fight infection.

inoculation: Introduction of material (i.e., vaccine, bacteria) into the bodyís tissues.font>

international importation of disease: Transmission of a disease from one country to another by way of an outside source (i.e., infected person or insect); or because a pathogen (bacterium or virus) has changed in a way that has either enabled it to avoid the immune system, or has made it stronger and more aggressive.

live vaccine: A vaccine that contains a living, yet weakened organism or virus.

microorganism: Living organisms or living things (plants or animals) so small in size that they are only visible by the aid of a microscope.

multi-drug resistance: The ability to withstand many antimicrobial drugs. For example, a new strain of pathogen may be resistant to many or all of the drugs that previously worked against the disease caused by the pathogen.

outbreak: Spread of disease, which occurs in a short period of time and in a limited geographic location (i.e., neighborhood, community, school, or hospital).

pandemic: An outbreak of disease that spreads throughout the world.font>

pathogen: Bacteria, viruses, parasites, or fungi that have the capability to cause disease in humans..

quarantine: To isolate an individual who has or is suspected of having a disease, in order to prevent spreading the disease to others; alternatively, to isolate a person who does not have a disease during a disease outbreak, in order to prevent that person from catching the disease. Quarantine can be voluntary or ordered by public health officials in times of emergency.

SSPE, or subacute sclerosing pan-encephalitis: Progressive, fatal destruction of nerve cells in the brain, which results in progressive deterioration of the personality, behavior, and intellectual abilities; seizures; coma, and death. For example, when measles or rubella virus infects brain cells, the immune system responds by attacking the virus. SSPE is the result of the immune systemís activity.

strain: A specific biologic version of a microorganism (i.e. bacterium or virus). The identity of a strain is defined by its genetic makeup, or code; changing just one piece of the code produces a new strain.

traveler's immunizations: A vaccination or series of vaccinations designed for people who travel to countries where certain diseases can be acquired. (www.cdc.gov/travel).

vaccination: Injection of a weakened or killed microorganism (bacterium or virus) given for the prevention or treatment of infectious diseases.

vaccine: A product of weakened or killed microorganism (bacterium or virus) given for the prevention or treatment of infectious diseases.

vaccine schedule: A chart or plan of vaccinations that are recommended for specific ages and/or circumstances.

virus:A tiny parasite that grows and reproduces in living cells. Vaccines prevent illnesses caused by the following viruses: Hepatitis B, Polio, Measles, Mumps, Rubella, Varicella, and Hepatitis A.

spacer

HHS Home | Questions? | Contact HHS | Accessibility | Privacy Policy | FOIA | Disclaimers

The White House | USA.gov | Helping America's Youth