Vaccination

United States President George W. Bush authorized a program on December 13, 2002, which by its conclusion, will see approximately 500,000 military personnel vaccinated against smallpox, along with an equal number of key healthcare providers in the United States. In the event of a biological attack that would expose Americans to smallpox, the affected citizens could then be quickly vaccinated by the protected healthcare workers. Additionally, the vaccine will be offered to up to ten million police, firefighters, and other first responders to emergencies. Smallpox vaccination within three days of exposure will usually prevent development of the disease, or dramatically reduce its virulence. Plentiful stocks are on hand in the U.S. to respond to a large smallpox outbreak, and vaccine in quantities necessary for inoculation of the entire population of the United States are in production. By mid-2004, health officials plan to have smallpox vaccinations available on a voluntary basis for all Americans.

An anthrax vaccine is also available and is only routinely given to laboratory workers who are involved with B. anthracis study or cultures. Vaccination for anthrax prevention involves a series of six injections over an 18-month period. Over 500,000 military personnel received the vaccine as a precaution in 2002, but for the general population, including medical providers and first responders, the vaccine is not currently recommended as other options such as antibiotic treatment offer protection to individuals exposed to anthrax-causing bacteria.

Diseases like anthrax and smallpox are among those microbial diseases that could be exploited as biological weapons. Indeed, anthrax was sent through the postal system to targets in the United States in the aftermath of the September 11, 2001 terrorist attacks in the U.S. Anthrax is a disease caused by the bacterium Bacillus anthracis , which can infect the skin, digestive tract, or lungs. Lung infection is often fatal. Smallpox is an extremely contagious disease that is caused by the variola virus.

Vaccination refers to the procedure in which the presence of a component of a microorganism such as a protein (the antigen) stimulates the defense mechanism of the host, which is known as the immune system, to form an antibody. Each antibody is formed in specific response to a particular antigen. The antibodies act to protect the host from future exposure to the antigen (immunity). Depending on the disease and the nature of the vaccine, the immunity can last from a year or two (i.e., influenza) to a lifetime.

Vaccination is protective against infection without the need of suffering through a bout of a disease. In this artificial process an individual receives the antibody-stimulating compound either by injection or orally. Some vaccines like that for smallpox do contain live microorganisms, which can cause some discomfort and, in rare cases, more serious complications. Nonetheless, for most people, vaccination is a prudent step to avoid the threat of a disease. As of early 2003, only one healthcare worker having received the recent smallpox vaccine reported a related complication, a non-life threatening vaccina rash. Less than a dozen instances of complication (none considered serious) have been reported among military personnel receiving the vaccine.

The technique of vaccination has been practiced since at least the early decades of the eighteenth century. Then, a common practice in Istanbul, Turkey was to retrieve material from the surface sores of a smallpox sufferer and rub the material into a cut on another person. The recipient was often spared the ravages of smallpox. This practice was noted by Lady Mary Wortley Montague, the wife of the British Ambassador Extraordinary to the Turkish court. Upon her return to England, she used her social standing to promote the benefits of this crude method of smallpox inoculation. Among those who were convinced was the Royal Family. Indeed, it became fashionable to receive an inoculation, partly perhaps it carried social cache. The technique was refined by Edward Jenner into a vaccine for cowpox in 1796.

Since Jenner's time, vaccines for a variety of bacterial and viral maladies have been developed. The material used for vaccination is one of four types. Some vaccines consist of living but weakened viruses. Such an attenuated vaccine does not cause an infection but does elicit an immune response. An example is the measles, mumps, and rubella (MMR) vaccine. The second type of vaccine can involve killed viruses or bacteria. The virus or bacteria need to be killed in a way that does not perturb their surfaces. This care is necessary to preserve the three-dimensional structure of surface molecules that stimulate the immune response. Agents such as alum can be used to enhance the immune response to the killed target, perhaps by exposing the antigen to the immune system for a longer time. A third type of vaccination involves a toxoid, which is an inactivated form of a toxin produced by the target bacterium. Examples of toxoid vaccines are the diphtheria and tetanus vaccines. Lastly, a biosynthetic vaccine can utilize a synthetic compound pieced together from portions of two antigens. The Hib vaccine is a biosynthetic vaccine.

Vaccinations against some diseases occurs early in life. For example, during an infant's first two years of life, a series of vaccinations is recommended to develop protection against hepatitis B, polio, measles, mumps, ru-bella (also called German measles), pertussis (also called whooping cough), diptheriae, tetanus (lockjaw), Haemophilus influenzae type b, pneumococcal infections, and chickenpox. Multiple injections of the vaccine can be required to ensure that the immunity that develops is long lasting. For example, vaccination against diphtheria, tetanus, and pertussis is typically administered at 2 months of age, 4 months, 6 months, 15 to 18 months, and finally at 4 to 6 years of age.

A series of vaccinations such as the above triggers a greater production of antibody by the immune system.

The immune cells that respond to the presence of an antigen in a vaccine are called lymphocytes. Prior to vaccination there are a multitude of lymphocytes, each of which recognizes a single specific protein or a portion of the protein. The presence of a specific antigen stimulates that lymphocyte that recognizes the antigenic target. That lymphocyte will then divide repeatedly and the daughter cells will produce antibody. Eventually, there are many daughter lymphocytes and a lot of antibody circulating in the body.

If the antigen does not persist in the body, the production of antibodies will stop. But the lymphocytes that have been produced still retain the memory of the target protein. When the target is presented again to the lymphocytes, as happens in the second vaccination in a series, the many lymphocytes are stimulated to divide into daughter cells, which in turn form antibodies. This is because the immune cells that responded to the antigen upon the first exposure "remember" the antigen, and so can produce even more antibody when presented with the antigen a second or third time. In immunological terms the immune cells are said to be "primed." This form of antigenic memory can last for a lifetime for diseases such as diphtheria and pertussis. For other diseases such as tetanus adults should be vaccinated every ten years (a "booster shot") in order to keep their bodies primed to fight the tetanus microorganism.

Many vaccinations are given via injection. However, solutions that can be drunk are also used. The classic example is the oral vaccine to polio devised by Albert Sabin. Oral vaccination is often limited by the passage of the vaccine through the highly acidic stomach. In the future is hoped that the bundling of the vaccine in a protective casing will prevent the damage caused in the stomach. Experiments using bags made out of lipid molecules (liposomes) has demonstrated both protection of the vaccine and the ability to tailor the liposome release of the vaccine.

While the benefits of vaccination are obvious, this protection against disease does not come without a risk. For a variety of vaccines, side effects are possible. For some vaccines, the side effects are minor. A person may, for example, develop a slight ache and redness at the site of injection. In some very rare cases, however, more severe reactions can occur, such as convulsions and high fever. The smallpox vaccine carries the risk of encephalitis (swelling of cells of the brain and spinal cord) in approximately three to 12 people per million people vaccinated.

█ FURTHER READING:

BOOKS:

Joellenbeck, Lois M., Lee L. Zwanziger, Jane S. Durch, and Brian L. Strom. The Anthrax Vaccine: Is It Safe? Does It Work? Washington: Joseph Henry Press, 2002.

Murphy, Christine. The Vaccine Dilemma. New York: Lantern Books, 2000.

Neustaedter, Randall. The Vaccine Guide: Risks and Benefits for Children and Adults. Berkeley: North Atlantic Books, 2002.

ELECTRONIC:

Centers for Disease Control and Prevention. "Vaccine Fact Sheets." National Vaccine Program Office. November 23, 2002. < http://www.cdc.gov/od/nvpo/fs_toc.htm >(6 January 2003).

SEE ALSO

Biocontainment Laboratories
Biological Warfare
Pathogens