Chances are you never had diphtheria. You probably don’t know anyone who has suffered from this disease, either. In fact, you may not know what diphtheria is. Similarly, diseases like whooping cough (pertussis), measles, mumps, and German measles (rubella) may be unfamiliar to you. In the 19th and early 20th centuries, these illnesses struck hundreds of thousands of people in India each year, mostly children, and tens of thousands of people died. The names of these diseases were frightening household words. Today, they are all but forgotten. That change happened largely because of vaccines.
Chances are you’ve been vaccinated against diphtheria. You may even have been exposed to the bacterium that causes it, but the vaccine prepared your body to fight off the disease so quickly that you were unaware of the infection. Vaccines take advantage of your body’s natural ability to learn how to combat many disease-causing germs, or microbes, that attack it. What’s more, your body “remembers” how to protect itself from the microbes it has encountered before. Collectively, the parts of your body that remember and repel microbes are called the immune system. Without the immune system, the simplest illness—even the common cold—could quickly turn deadly.
On average, your immune system takes more than a week to learn how to fight off an unfamiliar microbe. Sometimes that isn’t soon enough. Stronger microbes can spread through your body faster than the immune system can fend them off. Your body often gains the upper hand after a few weeks, but in the meantime you are sick. Certain microbes are so powerful, or virulent, that they can overwhelm or escape your body’s natural defenses. In those situations, vaccines can make all the difference.
Traditional vaccines contain either parts of microbes or whole microbes that have been killed or weakened so that they don’t cause disease. When your immune system confronts these harmless versions of the germs, it quickly clears them from your body. In other words, vaccines trick your immune system to teach your body important lessons about how to defeat its opponents.
Vaccine Benefits
Once your immune system is trained to resist a disease, you are said to be immune to it. Before vaccines, the only way to become immune to a disease was to actually get it and, with luck, survive it. This is called naturally acquired immunity. With naturally acquired immunity, you suffer the symptoms of the disease and also risk the complications, which can be quite serious or even deadly. In addition, during certain stages of the illness, you may be contagious and pass the disease to family members, friends, or others who come into contact with you.
Vaccines, which provide artificially acquired immunity, are an easier and less risky way to become immune. Vaccines can prevent a disease from occurring in the first place, rather than attempt to cure it after the fact.
Benefits for You and Others
It is also much cheaper to prevent a disease than to treat it. Vaccines protect not only yourself but also others around you. If your vaccine-primed immune system stops an illness before it starts, you will be contagious for a much shorter period of time, or perhaps not at all. Similarly, when other people are vaccinated, they are less likely to give the disease to you. Vaccines protect not only individuals but entire communities. That is why vaccines are vital to the public health goal of preventing diseases.
If a critical number of people within a community are vaccinated against a particular illness, the entire group becomes less likely to get the disease. This protection is called community, or herd, immunity. On the other hand, if too many people in a community do not get vaccinations, diseases can reappear. In 1989, low vaccination rates allowed a measles outbreak to occur in the United States. The outbreak resulted in more than 55,000 cases of measles and 136 measles-associated deaths.
