By Howard J. Bennett

The world is a dangerous place, and all living things need a way to protect themselves from outside invaders. But what you may not realize is that some of the biggest threats humans face come from the tiniest of enemies, specifically microscopic creatures known as viruses and bacteria.

The first line of defense against germs is the epidermis (top layer of skin) that keeps germs out of the body. Another front line of defense includes hairs and mucus in the nose and sinuses that trap viruses and bacteria. (The next time you pick your nose or spit out a glob of mucus, remind your mom that you are ridding yourself of nasty germs that are trying to make you sick! However, let me suggest that you dispose of your enemy in a tissue.)

If germs get through a person’s first lines of defense, the body has its own microscopic army to repel them. This army is made up of white blood cells that engulf the germs, chemicals that help the white blood cells find the germs, and more chemicals that help the body “remember” the germs so it can prevent or minimize an infection the next time that particular germ tries to attack you. This last line of defense is the process that enables vaccinations (shots) to work.

An English doctor named Edward Jenner, who lived from 1749 to 1823, is remembered as the Father of Vaccinations. During Jenner’s time, it had been observed that milkmaids were less likely to catch a deadly infection called smallpox. It was also known that milkmaids were more likely to catch a similar, but milder infection called cowpox. Jenner theorized that cowpox protected milkmaids from the more serious disease.

Although Jenner was not the first person to prevent smallpox, he was the first to scientifically prove that injecting people with a small amount of pus from a cowpox lesion would make them resistant to smallpox.

When your doctor gives you a vaccination, you are being injected with a tiny amount of a killed or weakened virus or bacteria. Because the organism is dead or damaged, it will not cause the disease. However, once this material is in your body, your immune system still springs into action and attacks the “invader.” In the process, your immune system makes antibodies (chemicals) that will mobilize your defenses if you come in contact with the actual germ at some point in the future.

Some vaccines only have to be given once to work. Others have to be given more than once either because the virus changes regularly (like with flu shots) or because it takes more than one shot for your body to make enough antibodies to be protected.

Vaccines are not 100% effective. They also can have side effects, which is why you sometimes get a sore arm or a fever after receiving a shot.

© 2012 Howard J. Bennett. All Rights Reserved.
(First published in the Washington Post 3/1/10.)

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please visit Dr. B’s website at  www.howardjbennett.com.