Prevention is crucial to good health. It's far better to prevent a disease than to treat it. One of the best ways to protect yourself and your family from many diseases is to get vaccinated. Immunization, another term for vaccination, is the best line of defense against diseases such as measles (rubeola), mumps, tetanus, hepatitis and polio. Immunization stimulates your body's natural defense mechanisms to resist infectious disease, destroying the virus before you become sick.
Thanks to vaccines, many infectious diseases that were once common in the United States are now rare or nonexistent. Parents no longer have to fear that their children will die of or become disabled by diphtheria, whooping cough (pertussis) or measles. Children don't have to keep away from water fountains and swimming pools to avoid getting polio.
Since coming into widespread use during the 20th century immunizations have saved billions of lives around the world. However, despite the availability of vaccines, many people remain underimmunized. One reason for this is that some parents have concerns about the safety and risks of vaccines. These concerns are often the result of incorrect information.
Every day, your body is threatened by bacteria, viruses and other germs. When a disease-causing microorganism enters your body, your immune system mounts a defense, producing proteins called antibodies to fight off the invader. The goal of your immune system is to neutralize or destroy the foreign invader, rendering it harmless and preventing you from getting sick.
Your body's immune system fights off foreign invaders and protects you from disease in the following two ways:
Post-exposure immunity
Post-exposure immunity develops after you've been exposed to a certain organism. Your immune system puts into play a complex array of defenses to prevent you from getting sick again from that type of virus or bacteria.
Exposure to a foreign invader (antigen) activates the production of certain white blood cells in your body called B cells (B lymphocytes). B cells produce plasma cells, which in turn produce a huge number of antibodies designed specifically to fight that particular invader. These antibodies circulate in your body's fluids, and the next time that invader enters your body, the antibodies recognize it and destroy it. Once your body produces a particular antibody, it can rapidly resume production of more if needed.
In addition to the work of B cells, white blood cells called macrophages confront and destroy foreign invaders. The macrophages "process" the invaders, figuring out if they present a threat. If your body encounters a germ that it has never been exposed to before, information about the germ is relayed to white blood cells called helper T cells. These cells aid in the development of other infection-fighting cells, including memory T cells.
Once you've been exposed to a specific virus or bacterium, the next time you encounter it, antibodies and memory T cells go to work. They immediately react to the organism, attacking it before disease can develop. Your immune system can recognize and effectively combat thousands, if not millions, of different organisms.
Vaccine immunity
Vaccine immunity results from injection of a vaccine. The vaccine triggers your immune system's infection-fighting ability and memory without exposure to the actual disease. A vaccine contains a killed or weakened form or derivative of the infectious germ. When given to an individual who's healthy, the vaccine triggers an immune response. The vaccine makes your body think that it's being invaded by a specific organism, and your immune system goes to work to destroy the invader and prevent it from infecting you again.
If you're exposed to a disease for which you've been vaccinated, the invading germs are met by antibodies prepared to destroy them. The immunity you develop following vaccination is similar to the immunity acquired from natural infection. For some diseases, the vaccine may be better at creating immunity than a natural infection would be. And vaccines can be administered without the risk of the serious effects of disease.
Several doses of a vaccine may be needed for a full immune response. Some people fail to build immunity to the first doses of a vaccine but often respond to later doses. In addition, the immunity provided by some vaccines, such as tetanus and pertussis, isn't lifelong. Because the immune response may decrease over time, you may need another dose of a vaccine (booster shot) to restore or increase your immunity.
Vaccines are prepared in several different ways. For each type, the goal is the same -- to stimulate an immune response without causing disease.
Live weakened
Some vaccines, such as those for measles, mumps and chickenpox (varicella), use live viruses that have been weakened (attenuated).
Killed or inactivated
Other vaccines use inactivated (killed) bacteria or viruses. The inactivated polio vaccine (IPV) is made this way.
Toxoid
Some types of bacteria cause disease by producing toxins that invade the bloodstream. Toxoid vaccines, such as those for diphtheria and tetanus, use bacterial toxins that have been rendered harmless.
Acellular and subunit
Acellular and subunit vaccines are made by using only part of the virus or bacteria. The hepatitis and Haemophilus influenzae type b (Hib) vaccines are made in this way.
Because many vaccine-preventable diseases are now uncommon in the United States, some people feel less urgency about getting themselves or their children immunized. Few people have ever seen a case of diphtheria, polio or tetanus. Some may feel that cleanliness and sanitation are enough to prevent disease.
If you wonder if it's necessary to keep up with immunizations, the answer is yes. Many infectious diseases that have virtually disappeared in the United States can reappear quickly, The germs that cause the diseases still exist and can be acquired by people who aren't protected by vaccination. As travelers unknowingly carry disease from one country to another, a new outbreak in the United States may be only a plane trip away. From a single entry point, an infectious disease can spread quickly among unprotected individuals.
The persistent threat of disease is just one reason public health officials recommend vaccinations. Vaccines provide a number of benefits to individuals, communities and the world population.
Mayo Clinic Family Health Book 3e. Copyright © by Susan Mayo Clinic. Reprinted by permission of HarperCollins Publishers, Inc. All rights reserved. Available now wherever books are sold.