See also: AIDS (acquired immunodeficiency syndrome), Anthrax, Chicken pox, Diphtheria, Encephalitis, German measles, Hemophilus influenzae, type B, Hepatitis B and similar diseases, Influenza, Measles (rubeola), Meningitis, Mumps, Pertussis, Poliomyelitis, Rabies, Smallpox, Syphilis, Tetanus, Tuberculosis,
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Vaccination and disease: Two hundred years ago the English physician Edward Jenner noticed that milkmaids frequently got a mild disease called cowpox from the cows in their care. But during smallpox epidemics these young women were protected and did not become ill. Jenner used these observations to develop vaccination.

How vaccination works People can become immune to a disease by becoming ill with the disease and surviving it. If the microorganisms causing the disease invade the body again, the immune system remembers and quickly destroys them without the person's becoming ill.
A vaccination accomplishes the same thing but more safely. The vaccination stimulates immunity to a disease by exposing the immune system to live, but weakened, organisms or to dead or inactivated organisms. In some modern vaccines genetically engineered analogs of parts of the germ are used to stimulate the nervous system. The immune system responds and creates a molecular memory of the disease organism, which is kept by special white blood cells. In a subsequent invasion by the same germ, the immune system causes these cells to multiply quickly and to produce a defense against the disease. As a result the vaccinated person either remains healthy or has only mild symptoms of the disease. Vaccination has some risks. Occasionally individuals develop symptoms related to the vaccination. Most common are allergic reactions to the medium in which the microorganisms are grown. People with problems of the immune system, such as AIDS, may not be able to have vaccinations made with live organisms.
Effective vaccinations have been developed to protect against many diseases, including smallpox, measles, mumps, chicken pox, tetanus, rubella, polio and diphtheria. Some vaccinations are given in a single dose, either orally or by injection, while others require multiple doses over a prescribed time period to provide maximum benefit. Most types of vaccination require a booster shot periodically as a kind of reminder to the immune system. Influenza vaccinations are given annually because each year different strains of influenza occur.

Vaccination requirements In the United States vaccination against childhood disease is required for entry into grade school (primary school). This public health requirement has dramatically reduced cases of measles, mumps, rubella, polio, diphtheria, tetanus, and pertussis (whooping cough). In the mid 1990s two new vaccinations were added: hepatitis and Hemophilus influenzae , type B (Hib). It was also recommended that children already in school be vaccinated against hepatitis B when they are 11 or 12 until all school-age children are vaccinated.
In underdeveloped and developing countries vaccinations have not been as available as in developed countries. In 1995 11 million children under the age of five died in undeveloped nations. Nine million of these deaths were due to infectious disease and 25% of these could have been prevented if the children had been vaccinated.

Future directions Vaccination is the single, most powerful method to control contagious diseases. New or improved vaccines are under research or development for tuberculosis, syphilis, HIV (AIDS), encephalitis, meningitis, and other diseases. New techniques, including genetic engineering, are being explored to develop better, safer, and less expensive vaccines.
Vaccination offers real hope for eliminating specific contagious disease from the planet. Smallpox, the deadly epidemic disease that killed millions and inspired Jenner, was declared eradicated in 1980. Global vaccination efforts may be able to repeat this achievement.
 

See also: AIDS (acquired immunodeficiency syndrome), Anthrax, Chicken pox, Diphtheria, Encephalitis, German measles, Hemophilus influenzae, type B, Hepatitis B and similar diseases, Influenza, Measles (rubeola), Meningitis, Mumps, Pertussis, Poliomyelitis, Rabies, Smallpox, Syphilis, Tetanus, Tuberculosis,
Back to the Index page