Immunizations - general overview

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Hepatitis A immunization (vaccine)

Immunizations

Immunization (vaccination) is a way to trigger your immune system and prevent serious, life-threatening diseases.

Vaccinations

Our bodies are designed to protect us from diseases. When you are exposed to an illness, your immune system actually learns from the experience. The next time your body is exposed to the same illness, your immune system often recognizes the culprit and sets out to destroy it.

Immunization exposes you to a very small, very safe amount of the most important diseases you are likely to encounter at some point in your life. This mild exposure helps your immune system recognize and attack the disease efficiently. If you are exposed to the full-blown disease later in life, you will either not become infected or have a much less serious infection. This is a natural way to deal with infectious diseases.

Throughout human history, infectious diseases have caused measureless misery and death. This rampage was unchecked until the twentieth century, when immunization was introduced on a wide scale. This led to the global eradication of smallpox, the elimination of polio from the Americas, and has almost eliminated tetanus, diphtheria, mumps, and the horrible congenital rubella syndrome. Immunization has greatly reduced the occurrence of measles, pertussis, and meningitis. Millions of deaths and other tragedies have been prevented.

Four different types of vaccines are currently available.

• Attenuated (weakened) live virus is used in the measles, mumps, and rubella (MMR) vaccine and the varicella (chicken pox) vaccine. These vaccines last longer than other vaccines, but may cause serious infections in people with compromised immune systems.
• Killed (inactivated) viruses or bacteria used in some vaccines. For example, the influenza vaccine uses killed virus. These vaccines are safe, even in people with compromised immune systems.
• Toxoid vaccines contain a toxin produced by the bacterium or virus. For example, the diphtheria and tetanus vaccines are actually toxoids.
• Biosynthetic vaccines contain synthetic "man-made" substances which appear to be antigens to the immune system. For example, the Hib (Haemophilus influenzae type B) conjugate vaccine is a biosynthetic vaccine.