| Benefits of Vaccines
Disease prevention is the key to public health. It is always better to prevent a
disease than to treat it. Vaccines prevent disease in the people who receive them and
protect those who come into contact with an unvaccinated individual. In the United
States, Federal and State public health programs help assure that children receive
vaccines. But vaccines are not just for young children. Adolescents and adults should
keep up-to-date on certain immunizations. Unvaccinated adults who did not have certain
childhood diseases should consider being immunized. And, people who travel overseas may
receive vaccines depending on their destinations.
Once scientists have identified the microorganism or toxin that causes an illness,
they pursue a number of approaches to develop a vaccine. All approaches to vaccine
development focus on the immune system and the body�s natural defenses against foreign
invaders. The immune system is a complex of organs and highly specialized cells and even
a circulatory system separate from blood vessels all of which work together to clear
infection from the body. The purpose of a vaccine is to bring about immunity by
provoking a response from a person�s immune system and creating a memory within the
immune system so that exposure to the active disease agent will stimulate an already
primed immune system to fight the disease.
Basic Research and Development
Basic research conducted and supported by the National Institutes of Health�s (NIH)
National Institute of Allergy and Infectious Diseases (NIAID), and basic and applied
research at the Food and Drug Administration�s (FDA) Center for Biologics Evaluation
and Research (CBER) are helping scientists understand more about infectious microbes and
human immune responses. From this understanding has come development of vaccines and
other tools needed to prevent many infectious diseases and immune system disorders. The
goal of these efforts is not only to protect individuals from serious infections, but
eventually to eradicate diseases, as we have done with smallpox.
Basic research focuses on the biological mechanisms disease-causing microbes use to
cause damage. Such research also takes into account physical characteristics of an
organism, which might be used as a vaccine component, or as a drug to prevent or
interrupt the disease process.
To develop a candidate vaccine, scientists first test preparations in cell-culture or
tissue-culture systems. If initial results are promising, the candidates are further
tested in laboratory animals such as mice, guinea pigs or even monkeys. In some cases,
computers can help researchers visualize the vaccine candidates in three dimensions to
predict how vaccines will interact with the immune system. If the vaccine candidate
performs well throughout these preclinical evaluations, it can become an investigational
vaccine for use in human volunteers in clinical trials.
Clinical Studies
Clinical studies rely upon the participation of thousands of people, from all walks
of life, who volunteer their time and energy to advance science and improve health care
for all. A typical volunteer in a vaccine study agrees to be given the vaccine, makes
frequent visits to a clinic for evaluation, participates in medical testing, and
provides blood or tissue samples that will be used in assessing the vaccine�s safety
and potential effectiveness. Research staff counsel volunteers about the study, and
volunteers must sign an informed consent document, indicating their understanding of the
study and their willingness to participate.
NIAID has designed a network of vaccine and treatment evaluation units, and more
recently, an international network for testing vaccines to prevent infection with HIV.
Testing sites are based at leading university medical research centers, public health
departments, and community clinics. Investigators working within these networks and
other NIAID-supported researchers play major roles in the clinical studies required for
licensing of vaccines.
A candidate vaccine undergoes three phases of clinical trials before it can be
considered for approval. Then FDA can approve a vaccine for general use if it is safe,
effective in preventing an infectious disease, and remains stable and potent during its
shelf life. The overall risk/benefit of a vaccine is critical in making a licensure
decision.
Side Effects and Adverse Reactions
No matter how extensive the testing, it is impossible to allow completely for the
infinite variation among individuals, their immune systems, and their reactions to the
introduction of new substances into their bodies. Serious systemic reactions to vaccines
can occur, although they are very rare. The FDA and the Centers for Disease Control and
Prevention (CDC) monitor vaccine distribution and use and collect information on adverse
reactions to vaccines, even after they are licensed for use by the general public.
Vaccines of the Future
Vaccines remain among the most powerful tools we have for disease prevention, and
advances in biotechnology have ushered in a new era in vaccine development that holds
even more promise for improving public health. Currently scientists are pursuing many
promising new strategies in vaccine development and exploring novel ways to administer
vaccines that may provide safer, more effective ways to fight disease.
NIH, National Institute of Allergy and Infectious Diseases: http://www.niaid.nih.gov/
Last updated: August 2001
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