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Disease prevention requires deliberate action, such as getting adequate sleep and exercise, dressing appropriately and washing our hands. It also requires an occasional shot in the arm.

Vaccines stop disease. They have dramatically altered the quality of life in America and have prevented millions of deaths here and around the world from diseases such as hepatitis B, measles and rubella.

The Immune System vs. Germs

Without any conscious effort on our part or medical intervention, the body can create its own defense against some infectious agents.

For example, when the virus that causes chickenpox invades a body, the immune system creates antibodies that bind to the virus and neutralize or inactivate it. While this is going on, memory B cells are produced and remain ready—often for a lifetime—to mount a quick, protective immune response against subsequent infection of the chickenpox virus.

So even though the number of antibodies created to fight the chickenpox virus subside, the memory B cells remain, forever on guard for that specific virus.

A vaccine causes a similar immune response. It is made from an antigen (a foreign substance that the body's immune system identifies as potentially harmful) from the chickenpox virus. The vaccine is injected into the fatty tissue. Memory B cells respond to the antigen by producing antibodies. As happens after an actual infection, the memory B cells remain ready to mount a quick protective immune response against subsequent infection by the chickenpox virus.

Vaccines exist for all sorts of diseases, both viral and bacterial. But not all diseases can be prevented by a vaccine. To date, scientists have been unable to develop vaccines against the viruses that cause the common cold, hepatitis C and HIV.

Efforts to create a vaccine against the common cold have failed because there are so many viruses that cause colds, and they are capable of mutating or changing so rapidly, antibodies that form to fight one cold virus don’t recognize the new or mutated virus and can’t fight it.

The hepatitis C virus and the human immunodeficiency virus remain challenges because they change ever so slightly every time they make copies of themselves. Developing a vaccine to fight one version of the hepatitis C virus would not work with the versions that have been slightly altered by replication. The same goes for the human immunodeficiency virus.

Perhaps one day scientists will be able to design vaccines that go after the common denominators in each virus, so that no matter what the slight variations are in each version, there will be some identifiers that won’t change and will therefore be susceptible to vaccines.

Influenza is another example where vaccines can only be given against specific forms of the virus. For a vaccine to be effective against a flu epidemic, it must be designed for that specific influenza strain. That is why a new vaccine is developed for each flu season. If you are exposed to a different flu virus from the one you are vaccinated for, you will still catch the flu.

Next Page: How Vaccines Work


Important disclaimer: The information on is for educational purposes only and should not be considered to be medical advice. It is not meant to replace the advice of the physician who cares for your child. All medical advice and information should be considered to be incomplete without a physical exam, which is not possible without a visit to your doctor.

Immunizations stop
disease from spreading.

Check with your family
doctor to see if you could benefit.