Vaccines 101

Chances are you or someone you know has never suffered from diphtheria, measles, mumps, rubella, polio or tetanus. Until the late 20th century, these illnesses affected hundreds of thousands of people in the United States, and thousands died. These illnesses are less common and fear provoking today as a result of vaccines.

Most likely you have been vaccinated against measles, mumps and rubella. There is also a chance that you have been exposed to the viruses that cause the illness, but because of the vaccine, your body was prepared to fight off the viruses before you even realized you were sick.

Vaccines contain either parts of microbes (bacteria or viruses) or whole microbes that have been killed or weakened so that they cannot cause disease. When a person is vaccinated, these microbes enter the body and stimulate the immune system to make antibodies that “remember” a virus or bacterium should it be encountered again. This enables the body to fight off the actual microbe quickly if it ever enters the body.

It takes one week on average for your immune system to fight off an unfamiliar microbe. Sometimes you may feel sick because your immune system cannot keep up with the spread of the microbe and because of the strong measures your immune system uses to fight the infection. Your body will eventually gain ground on the microbe and defeat it. Some microbes are very powerful or can escape the body’s natural defenses. In such cases, vaccines are very helpful.

You are said to be immune to a disease once your immune system is trained to recognize the disease or the antigen associated with the disease. Before vaccines, the only way to become immune to a disease was to actually get it, face all of the symptoms and survive. This process is known as naturally acquired immunity. In addition to suffering through the disease you may also be contagious and pass the disease to people in contact with you. Vaccines provide an artificial acquired immunity that trains the body to recognize the disease before it occurs in the first place, rather than attempting to cure the disease after the infection. The following chart shows how vaccines have been used to battle against specific diseases.

The Impact of Viral Vaccines in the United States

Disease Microbe Type Baseline 20th Century Pre-Vaccine Annual Cases 2008 Cases Percent Decrease
Measles Virus 503,282 55 99.9%
Mumps Virus 152,209 454 95.7%
Smallpox Virus 48,164 0 100%
Rubella Virus 47,745 11 99.9%
Polio Virus 16,316 0 100%

The Impact of Bacterial Vaccines in the United States

Disease Microbe Type Baseline 20th Century  Pre-Vaccine Annual Cases 2008 Cases Percent Decrease
Tetanus Bacteria 1,314 19 98.6%
Haemophilus influenzae type b, invasive Bacteria 20,000 30 99.9%
Pertussis Bacteria 147,271 10,735 92.7%
Diphtheria Bacteria 175,885 0 100%