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.
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.
Variations in individuals and their immune systems are many and subtle; thus no vaccine is totally effective. In the United States, a vaccine is approved for general use if it fulfills several stringent requirements.
- The vaccine must be safe. Although it is quite unlikely that a vaccine will ever be 100 percent safe, it must produce protective immunity with only minimal side
effects (such as redness and soreness at the vaccination site) for the overwhelming majority of those who receive it. More discomfort in side effects can be
acceptable, however, depending upon the severity of the disease the vaccine is designed to prevent. For example, most people would consider vaccine side effects
that mimicked the symptoms of a bad cold acceptable if the vaccine protected them from HIV disease.
- The vaccine must be immunogenic, that is, it must cause a strong and measurable immune response. Vaccines usually contain antigens, bits of material, sometimes from
the disease-causing microbe itself, that can stimulate the immune system to respond and fight off a potential infection. When a vaccine is immunogenic, it primes
the recipient’s immune system to recognize the disease-causing microbe and launch a counterattack before illness can occur. In addition, the vaccine must induce the
right type of immunity. When microbes invade, they cause disease in different ways, and different parts of the immune system respond to fight them. Vaccines must
stimulate the specific parts of the immune system that protect against a particular kind of organism.
- The vaccine must be stable during its shelf life, that is to say, its potency must remain at the proper level for the vaccine to evoke an immune response. Many
inactivated vaccines are simple to store, since they are in powdered form and are reconstituted with the appropriate fluid before they are given. Live, attenuated
vaccines, however, require refrigeration from manufacturer to clinic to maintain stability and potency.
All approaches to vaccine development focus on the immune system and the body’s natural defenses against foreign invaders. To understand something of how vaccines work,
it is best to start with the immune system. Together, your immune system and vaccines are powerful allies in the fight against disease.
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