glossary is maintained by CDC's National
Immunization Program (NIP) and only contains
terms associated with vaccines and vaccine-preventable
diseases. For information about other health
issues, see CDC's
"Health Topics A-Z".
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A vaccine containing partial cellular material
as opposed to complete cells.
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). This 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.
The production of antibodies against a specific
disease by the immune system. Active immunity
can be acquired in two ways, either by contracting
the disease or through vaccination. Active
immunity is usually permanent, meaning an individual
is protected from the disease for the duration
of their lives.
intense health effect.
A substance (e.g. aluminum salt) that is added
during production to increase the body's immune
response to a vaccine.
Undesirable experiences occurring after immunization
that may or may not be related to the vaccine.
Committee on Immunization Practices (ACIP)--
A panel of 10 experts who make recommendations
on the use of vaccines in the United States.
The panel is advised on current issues by representatives
from the Centers for Disease Control and Prevention,
Food and Drug Administration, National Institutes
of Health, American Academy of Pediatrics,
American Academy of Family Physicians, American
Medical Association and others. The recommendations
of the ACIP guide immunization practice at
the federal, state and local level.
in which the body has an exaggerated response
to a substance (e.g. food or drug). Also
known as hypersensitivity.
and severe allergic reaction to a substance
(e.g. food or drugs). Symptoms of anaphylaxis
include breathing difficulties, loss of consciousness
and a drop in blood pressure. This condition
can be fatal and requires immediate medical
An acute infectious disease caused by the spore-forming
bacterium Bacillus anthracis. Anthrax
most commonly occurs in hoofed mammals and
can also infect humans.
that fights bacteria.
A protein found
in the blood that is produced in response to
foreign substances (e.g. bacteria or viruses)
invading the body. Antibodies protect the body
from disease by binding to these organisms
and destroying them.
(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.
of destroying microorganisms including viruses
Literally "against-virus" -- any
medicine capable of destroying or weakening
A medical condition characterized
by inflammation of the joints which results
in pain and difficulty moving.
The degree to
which the occurrence of two variables or events
is linked. Association describes a situation
where the likelihood of one event occurring
depends on the presence of another event or
variable. However, an association between two
variables does not necessarily imply a cause
and effect relationship. The term association
and relationship are often used interchangeably.
See causal and temporal association.
A chronic medical
condition where the bronchial tubes (in the
lungs) become easily irritated. This
leads to constriction of the airways resulting
in wheezing, coughing, difficulty breathing
and production of thick mucus. The cause
of asthma is not yet known but environmental
triggers, drugs, food allergies, exercise,
infection and stress have all been implicated.
The presence of an infection without symptoms.
Also known as inapparent or subclinical infection.
A vaccine in which live virus is weakened through
chemical or physical processes in order to
produce an immune response without causing
the severe effects of the disease. Attenuated
vaccines currently licensed in the United States
include measles, mumps, rubella, polio, yellow
fever and varicella. Also known as a
A chronic developmental disorder usually diagnosed
between 18 and 30 months of age. Symptoms
include problems with social interaction and
communication as well as repetitive interests
and activities. At this time, the cause
of autism is not known although many experts
believe it to be a genetically based disorder
that occurs before birth.
Small white blood cells that help the body
defend itself against infection. These
cells are produced in bone marrow and develop
into plasma cells which produce antibodies.
Also known as B lymphocytes.
Tiny one-celled organisms present throughout
the environment that require a microscope to
be seen. While not all bacteria are harmful,
some cause disease. Examples of bacterial disease
include diphtheria, pertussis, tetanus, Haemophilus
influenza and pneumococcus (pneumonia).
Flaws in the
collection, analysis or interpretation of research
data that lead to incorrect conclusions.
A causal association (or relationship between
two factors) is consistent with existing medical
Soft tissue located within bones that produce
all blood cells, including the ones that fight
Additional doses of a vaccine needed periodically
to "boost" the immune system. For
example, the tetanus and diphtheria (Td) vaccine
which is recommended for adults every ten years.
neuritis-- Inflammation of nerves
in the arm causing muscle weakness and pain.
Development of a disease despite a person's
having responded to a vaccine.
The presence or absence of a variable (e.g.
smoking) is responsible for an increase or
decrease in another variable (e.g. cancer).
A change in exposure leads to a change in the
outcome of interest.
health condition-- A health related
state that lasts for a long period of time
(e.g. cancer, asthma).
That which can be transmitted from one person
or animal to another.
A chronic medical condition characterized by
inflammation of the bowel. Symptoms include
abdominal pain, diarrhea, fever, loss of appetite
and weight loss. The cause of Chron's
disease is not yet known, but genetic, dietary
and infectious factors may play a part.
Two or more vaccines administered at once in
order to reduce the number of shots given.
For example, the MMR (measles, mumps, rubella)
Capable of spreading
disease. Also known as infectious.
Having a large percentage of the population
vaccinated in order to prevent the spread of
certain infectious diseases. Even individuals
not vaccinated (such as newborns and those
with chronic illnesses) are offered some protection
because the disease has little opportunity
to spread within the community. Also known
as herd immunity.
The joining together of two compounds (usually
a protein and polysaccharide) to increase a
Inflammation of the mucous membranes surrounding
the eye causing the area to become red and
irritated. The membranes may be irritated
because of exposure to heat, cold or chemicals.
This condition is also caused by viruses, bacteria
in a recipient which is likely to result in
a life-threatening problem if a vaccine were
or Cot Death-- See Sudden Infant
Death Syndrome (SIDS).
A muscle in the upper arm where shots are usually
A medical condition where the myelin sheath
is damaged. The myelin sheath surrounds
nerves and is responsible for the transmission
of impulses to the brain. Damage to the
myelin sheath results in muscle weakness, poor
coordination and possible paralysis.
Examples of demyelinating disorders include
Multiple Sclerosis (MS), optic neuritis, transverse
neuritis and Guillain-Barre Syndrome (GBS).
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.
disease marked by the formation of a false
membrane, especially in the throat, which can
Sickness, illness or loss of health.
A measure used to describe how good a vaccine
is at preventing disease.
of the brain caused by a virus. Encephalitis
can result in permanent brain damage or death.
A general term describing brain dysfunction.
Examples include encephalitis, meningitis,
seizures and head trauma.
of disease within a specific geographical area
or population that is in excess of what is
low-level presence of disease in a community.
A medical condition characterized by inflammation
of the skin or mucous membranes (including
the mouth, throat and eyes). Erthema
Multiforme has been reported following infection.
Symptoms persist anywhere from 2 days to 4
weeks and include skin lesions, blisters, itching,
fatigue, joint pain and fever.
The cause of.
infectious agents (bacteria or viruses) in
a manner that promotes transmission and increases
the likelihood of disease.
Relating to fever; feverish.
Syndrome (GBS)-- A rare neurological
disease characterized by loss of reflexes and
temporary paralysis. Symptoms include
weakness, numbness, tingling and increased
sensitivity that spreads over the body.
Muscle paralysis starts in the feet and legs
and moves upwards to the arms and hands.
Sometimes paralysis can result in the respiratory
muscles causing breathing difficulties.
Symptoms usually appear over the course of
one day and may continue to progress for 3
or 4 days up to 3 or 4 weeks. Recovery
begins within 2-4 weeks after the progression
stops. While most patients recover, approximately
15%-20% experience persistent symptoms.
GBS is fatal in 5% of cases.
type b (Hib)-- A bacterial infection that may result in
severe respiratory infections, including pneumonia, and other diseases
such as meningitis.
A minor viral disease, that usually does not
persist in the blood; transmitted through ingestion
of contaminated food or water.
A viral disease transmitted by infected blood
or blood products, or thorugh unprotected sex
with someone who is infected.
is a liver disease caused by the Hepatitis
C virus (HCV), which is found in the blood
of persons who have the disease. HCV is spread
by contact with the blood of an infected person.
Hepatitis D-- is a defective virus
that needs the hepatitis B virus to exist.
Hepatitis D virus (HDV) is found in the blood
of persons infected with the virus.
is a virus (HEV) transmitted in much the same
way as hepatitis A virus. Hepatitis E, however,
does not often occur in the United States.
See Community immunity.
A disease characterized by painful skin lesions
that occur mainly on the trunk (back and stomach)
of the body but which can also develop on the
face and in the mouth. Complications
include headache, vomiting, fever and meningitis.
Recovery may take up to 5 weeks. Herpes
Zoster is caused by the same virus that is
responsible for chickenpox. Most people
are exposed to this virus during childhood.
After the primary infection (chickenpox), the
virus becomes dormant, or inactivated.
In some people the virus reactivates years,
or even decades, later and causes herpes zoster.
Also known as the shingles.
The eruption of red marks on the skin that
are usually accompanied by itching. This
condition can be caused by an allergy (e.g.
to food or drugs), stress, infection or physical
agents (e.g. heat or cold). Also known
A condition in which the body has an exaggerated
response to a substance (e.g. food or drug).
Also known as an allergy.
A condition in which the body has a weakened
or delayed reaction to a substance.
A protein found in the blood that fights infection.
Also known as gamma globulin.
complex system in the body responsible for
fighting disease. Its primary function is to
identify foreign substances in the body (bacteria,
viruses, fungi or parasites) and develop a
defense against them. This defense is known
as the immune response. It involves production
of protein molecules called antibodies to eliminate
foreign organisms that invade the body.
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.
by which a person or animal becomes protected
against a disease. This term is often used
interchangeably with vaccination or inoculation.
When the immune
system is unable to protect the body from disease.
This condition can be caused by disease (like
HIV infection or cancer) or by certain drugs
(like those used in chemotherapy). Individuals
whose immune systems are compromised should
not receive live, attenuated vaccines.
vaccine-- A vaccine made from viruses
and bacteria that have been killed through
physical or chemical processes. These
killed organisms cannot cause disease.
The presence of infection without symptoms.
Also known as subclinical or asymptomatic infection.
The number of
new disease cases reported in a population
over a certain period of time.
The time from contact with infectious agents
(bacteria or viruses) to onset of disease.
Capable of spreading
disease. Also known as communicable.
Organisms capable of spreading disease (e.g.
bacteria or viruses).
Redness, swelling, heat and pain resulting
from injury to tissue (parts of the body underneath
the skin). Also known as swelling.
Bowel Disease (IBD)-- A general term
for any disease characterized by inflammation
of the bowel. Examples include colitis
and Crohn's disease. Symptoms include
abdominal pain, diarrhea, fever, loss of appetite
and weight loss.
A highly contagious
viral infection characterized by sudden onset
of fever, severe aches and pains, and inflammation
of the mucous membrane.
A vaccine that has been approved by the Food
and Drug Administration (FDA) for use in clinical
trials on humans. However, investigational
vaccines are still in the testing and evaluation
phase and are not licensed for use in the general
Yellowing of the eyes. This condition
is often a symptom of hepatitis infection.
An abnormal change in the structure of an organ,
due to injury or disease.
vaccine-- A vaccine in which
live virus is weakened through chemical or
physical processes in order to produce an immune
response without causing the severe effects
of the disease. Attenuated vaccines currently
licensed in the United States include measles,
mumps, rubella, polio, yellow fever and varicella.
Also known as an attenuated vaccine.
A disease characterized by inflammation of
the connective tissue (which supports and connects
all parts of the body). Chronic swelling
of the connective tissue causes damage to the
skin, joints, kidneys, nervous system and mucous
membranes. The disease begins with fever,
joint pain and fatigue. Additional
symptoms continue to develop over the years
including nausea, fatigue, weight loss, arthritis,
headaches and epilepsy. Problems with
heart, lung and kidney function may also result.
This condition is diagnosed most frequently
in young women but also occurs in children.
A bacterial disease transmitted by infected ticks. Human beings
may come into contact with infected ticks during outdoor activities
(camping, hiking). Symptoms include fatigue, chills, fever,
headache, joint and muscle pain, swollen lymph nodes and a skin
rash (in a circular pattern). Long-term problems include arthritis,
nervous system abnormalities, irregular heart rhythm and meningitis.
Lyme disease can be treated with antibiotics. A vaccine was
available from 1998 to 2002.
Small white blood cells that help
the body defend itself against infection.
These cells are produced in bone marrow and
develop into plasma cells which produce antibodies.
Also known as B cells.
A large cell that helps the body defend itself
against disease by surrounding and destroying
foreign organisms (viruses or bacteria).
Skin lesions, normally red-colored.
viral disease marked by the eruption of red
circular spots on the skin.
Cell-- A group of cells that help
the body defend itself against disease by remembering
prior exposure to specific organisms (e.g.
viruses or bacteria). Therefore these
cells are able to respond quickly when these
organisms repeatedly threaten the body.
Inflammation of the brain and spinal cord that
can result in permanent brain damage and death.
in joe en sef uh LIGHT iss"] -- inflammation
of the brain and meninges (membranes) that
involves the encephalon (area inside the skull)
and spinal column.
Tiny organisms (including viruses
and bacteria) that can only be seen with a
membranes-- The soft, wet tissue that
lines body openings specifically the mouth,
nose, rectum and vagina.
sclerosis is a disease of the central nervous
system characterized by the destruction of
the myelin sheath surrounding neurons, resulting
in the formation of "plaques." MS
is a progressive and usually fluctuating disease
with exacerbations (patients feeling worse)
and remissions (patients feeling better) over
many decades. Eventually, in most patients,
remissions do not reach baseline levels and
permanent disability and sometimes death occurs.
The cause of MS is unknown. The most widely
held hypothesis is that MS occurs in patients
with a genetic susceptibility and that some
environmental factors "trigger" exacerbations.
MS is 3 times more common in women than men,
with diagnosis usually made as young adults.
Also see demyelinating disorders.
viral illness marked by swelling, especially
of the parotid glands.
Inflammation of the nerves.
A general term
for any dysfunction in the peripheral nervous
system. Symptoms include pain, muscle
weakness, numbness, loss of coordination and
paralysis. This condition may result
in permanent disability.
A medical condition where vision deteriorates
rapidly over hours or days. One or both
eyes may be affected. This condition
results for the demyelination of optic nerves.
In most cases, the cause of optic neuritis
is unknown. Patients may regain their
vision or be left with permanent impairment.
Also see demyelinating disorders.
of mumps infection occurring in males (who
are beyond puberty). Symptoms begin 7-10
days after onset of mumps and include inflammation
of the testicles, headache, nausea, vomiting,
pain and fever. Most patients recover
but in rare cases sterility occurs.
A viral or bacterial infection that leads to
inflammation of the middle ear. This
condition usually occurs along with an upper
respiratory infection. Symptoms include
earache, high fever, nausea, vomiting and diarrhea.
In addition, hearing loss, facial paralysis
and meningitis may result.
of a disease in a specific geographic area
(e.g. neighborhood or community) or population
An epidemic occurring over a very large
Marked by small red-colored elevation of the
Protection against disease through antibodies
produced by another human being or animal.
Passive immunity is effective, but protection
is generally limited and diminishes over time
(usually a few weeks or months). For example,
maternal antibodies are passed to the infant
prior to birth. These antibodies temporarily
protect the baby for the first 4-6 months of
bacteria, viruses, parasites and fungi) that
cause disease in human beings.
(whooping cough) Bacterial infectious disease
marked by a convulsive spasmodic cough, sometimes
followed by a crowing intake of breath.
["pe TEEK ee ay"] -- a tiny reddish
or purplish spot on the skin or mucous membrane,
commonly part of infectious diseases such as
A substance or treatment that has no effect
on human beings.
Inflammation of the lungs characterized by
fever, chills, muscle stiffness, chest pain,
cough, shortness of breath, rapid heart rate
and difficulty breathing.
(polio) An acute infectious viral disease characterized
by fever, paralysis, and atrophy of skeletal
vaccines-- Vaccines that are composed 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
A measure of strength.
in a recipient which may result in a life-threatening
problem if the vaccine is given, or a condition
which could compromise the ability of the vaccine
to produce immunity.
The number of
disease cases (new and existing) within a population
over a given time period.
An early symptom indicating the onset of an
attack or a disease.
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.
Of or resulting from new combinations of genetic
material or cells; the genetic material produced
when segments of DNA from different sources
are joined to produce recombinant DNA.
Syndrome-- Encephalopathy (general
brain disorder) in children following an acute
illness such as influenza or chickenpox.
Symptoms include vomiting, agitation and lethargy.
This condition may result in coma or death.
Seizure Disorder (RSD)-- See
that an individual will experience a certain
A group of viruses that cause diarrhea in children.
(German measles) Viral infection that is milder
than normal measles but as damaging to the
fetus when it occurs early in pregnancy.
Development of antibodies in the blood of an
individual who previously did not have detectable
Measurement of antibodies, and other immunological
properties, in the blood serum.
Study measuring a person's risk of developing
a particular disease.
The sudden onset of a jerking and staring spell
usually caused by fever. Also known as
See herpes zoster.
Undesirable reaction resulting from immunization.
An acute, highly infectious, often fatal disease
caused by a poxvirus and characterized by high
fever and aches with subsequent widespread eruption
of pimples that blister, produce pus, and form
pockmarks. Also called variola.
A specific version
of an organism. Many diseases, including HIV/AIDS
and hepatitis, have multiple strains.
The presence of infection without symptoms.
Also known as inapparent or asymptomatic infection.
Infant Death Syndrome (SIDS)-- The
sudden and unexpected death of a healthy infant
under 1 year of age. A diagnosis of SIDS
is made when an autopsy cannot determine another
cause of death. The cause of SIDS is
unknown. Also known as "crib"
or "cot" death.
Two or more events that occur around the same
time but are unrelated, chance occurrences.
Of, relating to, or causing developmental malformations.
Toxin-producing bacterial disease marked by
painful muscle spasms.
Thimerosal is a mercury-containing preservative
that has been used in some vaccines and other
products since the 1930's. There is no evidence
that the low concentrations of thimerosal in
vaccines have caused any harm other than minor
reactions like redness or swelling at the injection
site. However, in July 1999 the U.S. Public
Health Service, the American Academy of Pediatrics,
and vaccine manufacturers agreed that thimerosal
should be reduced or eliminated from vaccines
as a precautionary measure. Today, all routinely
recommended childhood vaccines manufactured
for the U.S. market contain either no thimerosal
or only trace amounts.
of antibodies in blood through a laboratory
Myelitis-- The sudden onset of spinal
cord disease. Symptoms include general
back pain followed by weakness in the
feet and legs that moves upward. There
is no cure and many patients are left with
permanent disabilities or paralysis.
Transverse Myelitis is a demyelinating disorder
that may be associated with Multiple Sclerosis
(MS). Also see demyelinating disorders.
The eruption of red marks on the
skin that are usually accompanied by itching. This condition
can be caused by an allergy (e.g. to food or drugs), stress, infection
or physical agents (e.g. heat or cold). Also known as hives.
a killed or weakened infectious organism in
order to prevent the disease.
A product that
produces immunity therefore protecting the
body from the disease. Vaccines are administered
through needle injections, by mouth and by
Adverse Event Reporting System (VAERS)--
A database managed
by the Centers for Disease Control and Prevention
and the Food and Drug Administration. VAERS
provides a mechanism for the collection and
analysis of adverse events associated with
vaccines currently licensed in the United States.
Reports to VAERS can be made by the vaccine
manufacturer, recipient, their parent/guardian
or health care provider. For more information
on VAERS call (800) 822-7967.
Safety Datalink Project (VSD)--
In order to
increase knowledge about vaccine adverse events,
the Centers for Disease Control and Prevention
have formed partnerships with eight large health
Management Organizations (HMOs) to continually
evaluate vaccine safety. The project contains
data on more than 6 million people. Medical
records are monitored for potential adverse
events following immunization. The VSD project
allows for planned vaccine safety studies as
well as timely investigations of hypothesis.
-- An acute contagious disease characterized
by papular and vesicular lesions.
Characterized by small elevations of the skin
containing fluid (blisters).
The presence of a virus in the blood.
The relative capacity of a pathogen to overcome body defenses.
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.
The loss of protective
antibodies over time.
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