views updated



Vaccination is the injection of a weakened or dead disease—producing organism in a person to provide immunity against the disease caused by the organism.


Many microorganisms, such as viruses and bacteria, can infect humans and produce disease. The body's defense mechanism against these foreign invaders is the immune system which can produce antibodies to neutralize or destroy the disease-carrying organisms (pathogens) and the toxins that they produce. When a person's immune system has produced antibodies against a specific pathogen after being exposed to it, the person is said to have achieved natural immunity to that pathogen. If this person comes into contact with that same pathogen in the future, the immune system will immediately recognize it and produce the antibodies required to fight it. Besides having the immune system of a person produce antibodies upon exposure to a real pathogen, another way to provide immunity is to inject a person with a killed or weakened form of the disease organism through vaccination. This is called vaccine-induced immunity, and will trigger the same antibody-producing immune response from the person's body. A preparation of weakened or killed pathogen is called a vaccine. The advantage of vaccination is that it stimulates antibody production against the pathogen and provides immunity, but does not cause severe infection.

Vaccines recommended for adults over 50
source: Centers for Disease Control and Prevention, U.S.
Department of Health and Human Services
(Illustration by GGS Information Services. Cengage Learning,
Tetanus-diphtheria (Td)Booster every 10 years, especially after age 50
Influenza (Flu)After age 50, every year
PneumoniaA single dose around age 65. If you have lung,
heart, or kidney disease, HIV, diabetes, or cancer,
you may need this shot sooner
Herpes Zoster (Shingles)A single dose for adults 60 years old or older who
have already had chickenpox but who have not
had shingles
Hepatitis ARecommended if you have long-term liver disease,
receive blood products to help your blood clot,
or travel to countries with high rates of
hepatitis A
Hepatitis BRecommended if you are a dialysis patient or have
end-stage kidney disease, have HIV infection,
have chronic liver disease, or travel to countries
with intermediate or high rates of hepatitis B
virus infection

Antibodies are disease-specific. For example, antibodies produced against the virus that causes measles will protect a person who is exposed to the virus, but will have no effect if the person is exposed to the hepatitis virus. This is why there are so many different types of vaccines.


The purpose of vaccination is to immunize people against specific pathogens to protect them from disease and also to eliminate disease. As more and more people are vaccinated, specific disease are eradicated, as for example polio and diphtheria in the United States.

Children are routinely given a series of vaccinations starting at birth. Given according to a specific schedule, they immunize against hepatitis A and B,


Active immunity —Protection against a disease that results when exposure to a disease organism triggers the immune system to produce antibodies to that disease.

Anthrax —An infectious disease caused by a type of bacterium. The disease can be passed from animals to people and usually is fatal. Symptoms include sores on the skin.

Antibody —Proteins produced by the body to neutralize or destroy toxins or disease-carrying organisms.

Bacteria —Tiny, single-celled forms of life that cause many diseases and infections.

Cholera —An infection of the small intestine caused by a type of bacterium. The disease is spread by drinking water or eating seafood or other foods that have been contaminated with the feces of infected people. It occurs in parts of Asia, Africa, Latin America, India, and the Middle East. Symptoms include watery diarrhea and exhaustion.

Cowpox —A mild disease in cows that is caused by a poxvirus.

Diphtheria —A serious, infectious disease that produces a toxin (poison) and an inflammation in the membrane lining of the throat, nose, trachea, and other tissues.

Encephalitis —Inflammation of the brain, usually caused by a virus. The inflammation may interfere with normal brain function and may cause seizures, sleepiness, confusion, personality changes, weakness in one or more parts of the body, and even coma.

Immune system —The immune system consists of the organs and cells of the lymphatic system that protect the body against infections and other diseases.

Immunization —A technique used to cause an immune response that results in resistance to a specific disease, especially an infectious disease. A vaccination is a type of immunization.

Immune —Resistant to an infectious disease.

Influenza —A serious disease caused by viruses that infect the respiratory tract.

Measles —An acute and highly contagious viral disease marked by distinct red spots followed by a rash that occurs primarily in children.

Meningitis —Inflammation of tissues that surround the brain and spinal cord.

Microorganism —An organism that is too small to be seen with the naked eye.

Mumps —An acute and highly contagious viral illness that usually occurs in childhood.

Natural immunity —Protection against a disease that results when exposure to a real disease organism triggers the immune system to produce antibodies to that disease.

Pathogen —A disease—causing microorganism.

Passive immunity —Protection against a disease that is provided when a person is given antibodies to a disease rather than producing them through his or her own immune system.

Plague —A highly infectious disease that can be fatal if not treated promptly. The bacteria that cause plague mainly infect rats, mice, squirrels, and other wild rodents. The disease is passed to people through fleas. Infected people can then spread the disease to other people.

Rabies —A rare but serious disease caused by a virus carried in saliva. It is transmitted when an infected animal bites a person.

Rubella —A contagious viral disease that is milder than typical measles but is damaging to the fetus when it occurs early in pregnancy. Also called German measles.

Smallpox —A highly contagious viral disease characterized by fever and weakness and skin eruption with pustules that form scabs that slough off leaving scars.

Tuberculosis —An infectious disease that usually affects the lungs, but may also affect other parts of the body. Symptoms include fever, weight loss, and coughing up blood.

Typhoid fever —An infectious disease caused by a type of bacterium. People with this disease have a lingering fever and feel depressed and exhausted. Diarrhea and rose—colored spots on the chest and abdomen are other symptoms. The disease is spread through poor sanitation.

Vaccination —Injection of a killed pathogen in order to stimulate the immune system against the pathogen.

Vaccine —A preparation of a weakened or killed pathogen, such as a bacterium or virus, that upon administration to a person stimulates antibody production against the pathogen but is incapable of causing severe infection.

Vaccine—induced immunity —Protection against a disease that results when exposure to a dead or weakened disease organism triggers the immune system to produce antibodies to that disease.

Virus —A tiny, disease-causing particle that can reproduce only in living cells.

Whooping cough —An infectious disease, also called pertussis, especially of children that is caused by a bacterium and is marked by a convulsive, spasmodic cough, sometimes followed by a shrill intake of breath.

Yellow fever —An infectious disease caused by a virus. The disease, which is spread by mosquitoes, is most common in Central and South America and Central Africa. Symptoms include high fever, jaundice (yellow eyes and skin) and dark—colored vomit, a sign of internal bleeding. Yellow fever can be fatal.

diphtheria, tetanus, whooping cough, measles, mumps, German measles (rubella), chickenpox (varicella), polio, pneumococcus and Haemophilus influenzae type b, which causes Hib disease with associated spinal meningitis . This series of vaccinations is recommended by the American Academy of Family Physicians (AAFP), the American Academy of Pediatrics (APA), and the Centers for Disease Control and Prevention (CDC). It is required in all states before children can attend school. Exceptions are made for children who have medical conditions such as cancer that prevent them from having vaccinations, and some states also will make exceptions for children whose parents object for various reasons. Some vaccines are combined in one injection, such as the measles-mumps-rubella (MMR) or diphtheria-pertussis-tetanus (DPT) combinations.

In addition to the childhood vaccination schedule, vaccines are available for preventing anthrax, cholera, Japanese encephalitis, meningococcal meningitis, plague, pneumococcal infection (meningitis, pneumonia ), tuberculosis , typhoid fever, and yellow fever. Most vaccines are given as injections, but a few are given by mouth.

Vaccines are also given for targeted purposes. Some, such as the rabies vaccine, are given only when a person is likely to have been exposed to the virus that causes the disease—through a dog bite, for example. Others are given to travelers planning to visit countries where certain diseases are common such as typhoid fever or yellow fever. Vaccines such as the influenza vaccine, also called “flu shots,” are given mainly to specific groups of people—older adults and others, who are considered at high risk of developing influenza or its complications.

Influenza vaccination policy in most high-income countries attempts to reduce the mortality burden of influenza by targeting people aged at least 65 years for vaccination. However, the effectiveness of this strategy is being debated. Trials have shown that influenza vaccine is effective in younger adults, but few trials have included elderly people, and especially those aged at least 70 years, the age group that accounts for 75% of all influenza-related deaths.


To administer a vaccine, a sterile needle is fitted into a syringe. The vaccine is withdrawn from a single dose vial or a single dose is taken from a multidose vial. The vaccine is always administered shortly after withdrawal from the vial by injection.


Vaccines are stored in refrigerated units at a temperature of 35°46°F (2°–8°C). Before administration, they are carefully checked for extraneous particulate matter and/or discoloration.


Vaccines are administered by trained health practitioners. The Association for Prevention Teaching and Research (APTR), in collaboration with the University of Pittsburgh School of Medicine and the Centers for Disease Control distribute Teaching Immunization for Medical Education (TIME) modules to medical schools that can be integrated into existing medical courses. The modules include vaccine indications and contraindications, immunization schedules, and recommendations on efficient ways to increase vaccination levels.



Crosby, Molly C. The American Plague: The Untold Story of Yellow Fever, the Epidemic that Shaped Our History. New York: Berkley Books (Penguin Group), 2006.

Jenner, Edward, ed. The Three Original Publications on Vaccination Against Smallpox. Whitefish: Kessinger Publishing, 2005.

Offit, Paul A. The Cutter Incident: How America's First Polio Vaccine Led to the Growing Vaccine Crisis. New Haven: Yale University Press, 2007.

Offit, Paul A. Vaccinated: One Man's Quest to Defeat the World's Deadliest Diseases. New York: Collins, 2007.

Romm, Aviva J. Vaccinations: A Thoughtful Parent's Guide: How to Make Safe, Sensible Decisions about the Risks, Benefits, and Alternatives. Rochester: Healing Arts Press, 2001.


Aspinall, R., Del Giudice, G., Effros, R. B., Grubeck-Loebenstein, B., Sambhara, S. “Challenges for vaccination in the elderly.” Immunity & Ageing 4, no. 1 (December 2007): 9.

El Yousfi, M., et al. “The inflammatory response to vaccination is altered in the elderly.” Mechanisms of Ageing and Development 126, no. 8 (August 2005): 874–881.

Kasten, M. J., and G. A. Poland. “Influenza vaccination and the elderly: pandemic preparedness.” Drugs & Aging 25, no. 3 (2008): 179–186.

Kovaiou, R. D., et al. “Age—related changes in immunity: implications for vaccination in the elderly.” Expert Reviews in Molecular Medicine 9, no. 3 (February 2007): 1–17.


Adults With Asthma Should Receive Flu Vaccination. CDC, Information Page (March 30, 2008)

Combination Vaccines. NNII Immunization Issues, Information Page (March 30, 2008)

How do I know if the vaccine information I find on the Internet is accurate? NNII Immunization Issues, Information Page (March 30, 2008)

Immunization. Medline Plus, Health Topics (March 30, 2008)

Questions and Answers about Vaccination. Health Canada, Information Page (March 30, 2008)

What You Need to Know About Vaccinations and Travel: A Checklist. CDC Vaccinations, Information Page (March 30, 2008)


Centers for Disease Control and Prevention (CDC), 1600 Clifton Road NE, MS-C09, Atlanta, GA, 30333, (404) 498-1515, (800)311-3435,

National Institute of Allergy and Infectious Diseases (NIAID), 6610 Rockledge Drive, MSC 6612, Bethesda, MD, 20892-6612, (301)496-5717, (866)284-4107,

National Network for Immunization Information, 301 University Blvd., CH 2.218, Galveston, TX, 77555 0351, (409)772-0199, [email protected],

National Vaccine Program Office. U.S. Department of Health & Human Services, 200 Independence Ave., SW, Washington, DC, 20201, (202)619-0257, (877)696 6775, [email protected],

Monique Laberge Ph.D.