Understanding Vaccines
National Institutes of Health
National Institute of Allergy and Infectious Diseases
More than two hundred years ago, Edward Jenner, a country physician practicing in England, noted that milkmaids rarely suffered from smallpox, a disease that was known to kill up to 40 percent of those who contracted it. The milkmaids often did get cowpox, a related but far less serious disease, and those who did never became ill with smallpox. In an experiment that was to prove a revelation, Jenner took a few drops of fluid from a skin sore of a woman who had cowpox and injected the fluid into the arm of a healthy young boy who had never had cowpox or smallpox. Six weeks later, Jenner injected the boy with fluid from a smallpox sore, but the boy remained free of the dreaded smallpox. Dr. Jenner had discovered one of the fundamental principles of immunization. He had used a relatively harmless foreign substance to evoke an immune response that would protect someone from a disease causing microbe.
In those days, a million people died from smallpox each year in Europe alone, most of them children. Those who survived were often left with grim reminders of their ordeals: blindness, deep scars, deformities. When Jenner laid the foundation for modern vaccines in 1796, he started on a course that would ease the suffering of people around the world. By the beginning of this century, vaccines for rabies, diphtheria, typhoid fever and plague were in use, in addition to the vaccine for smallpox.
Yet vaccination was not immediately accepted. The idea of deliberately introducing a potentially harmful microbe into people was met with suspicion and even outrage by many in the medical and scientific communities, and public opinion was bitterly divided over the merits of vaccination. It took some time to convince people that the benefits of vaccination outweigh the few risks. Today's vaccines are far safer and more protective than those early vaccines. And as science advances, we are developing even better vaccines to protect ourselves from disease.
Benefits
Disease prevention is the key to public health. Vaccines benefit in particular the people who receive them, and in turn, those people cannot spread disease to others who have not been vaccinated. Infection
cannot spread if it never gains a foothold. Infectious diseases cause enormous suffering, strain the capabilities of our health care system, and deplete financial resources. For the individual, the health care provider, and in the interest of conserving human and financial resources, it is always better to prevent a disease than to treat it.
Veterinary vaccines benefit people, too. Some diseases, such as rabies, anthrax, certain types of encephalitis, and Rift Valley fever, are readily transmissible from animal species to humans. In many instances, livestock and pets are vaccinated not only for their own health, but for that of their owners.
In the United States, federal and state public health programs help assure that children receive vaccines. Many childhood diseases that were a normal part of growing up just 50 years ago are now preventable. Measles, rubella (German measles), mumps, pertussis, (whooping cough), and chickenpox were almost unavoidable. Most people did not reach adulthood without their families or circle of friends being touched by a serious illness or death caused by an infectious disease. For the most part, children suffered through the course of the disease and were left with naturally acquired immunity, some school work to catch up on, and perhaps a little pockmark somewhere on their skin. However, in some cases, children died, or they were left with permanent loss of hearing or sight or other tragic effects of serious infections.
Adult Immunization
Although most of us receive the great majority of our immunizations during childhood, it is important to remember that vaccines are not just for young children. Adolescents and adults should keep up-to-date on tetanus and diphtheria immunizations. Adults who have not had diseases such as measles or chickenpox during childhood, or the vaccines to prevent them, should consider being immunized. Ironically, childhood diseases such as measles, mumps, and chickenpox can be far more serious in adults.
People who travel overseas should determine, together with their physicians or at international travel clinics, which vaccines would be appropriate based on their destinations. Effective vaccines are available to prevent yellow fever, polio, typhoid fever, hepatitis A, cholera, and other bacterial and viral diseases that are more prevalent abroad than in the United States.
Each year, as we prepare for winter and the flu season, many adults should consider the benefits of the flu vaccine. In addition to flu vaccine, immunizations for pneumococcal pneumonia, hepatitis A, and hepatitis B are recommended for people who may be at risk.
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