Vaccination has eradicated smallpox worldwide and prevents such diseases as cholera, rabies, and typhoid fever. Vaccines work with the immune system's ability to recognize and destroy foreign proteins (antigens) that it determines are "nonself." Scientists are using this same principle to help the body recognize antigens peculiar to cancer cells. It is also applied in an experimental birth control vaccine that tricks the immune system into believing that human chorionic gonadotropin (HCG), a hormone secreted by a developing fertilized egg, is foreign, thus inactivating it and inducing menstruation even if fertilization has occurred. Vaccines are also used to control animal pests by conferring temporary infertility.
Vaccination programs have been notably successful in the United States. For example, in 1998 the Centers for Disease Control and Prevention reported only one case of poliomyelitis, one of diphtheria, 34 of tetanus, and 89 of measles. Despite the availability of vaccines, many thousands of people in the United States still die each year from vaccine-preventable diseases such as hepatitis and influenza.
Immunization against 17 diseases is recommended for young children and adolescents: hepatitis B (HepB); rotavirus; diphtheria, tetanus (lockjaw), and pertussis (whooping cough), given together as DTaP (formerly DTP) and, for older children, Tdap; Haemophilus influenzae b (Hib); poliomyelitis (IPV); pneumococcal infections, including pneumonia, meningitis, and bacteremia (PCV and PPV); measles, mumps, and rubella, given together as MMR; chicken pox (Var); hepatitis A (HepA); influenza; Neisseria meningitidis (meningococcal meningitis; MCV4, MPSV4); and, for girls only, human papillomavirus (HPV). Researchers are working to develop combination vaccines that would simplify vaccine administration. Immunization against diseases such as yellow fever may be necessary before traveling to some countries. In 2002 the U.S. government decided to reinstitute smallpox vaccination for many military, health-care, and emergency personnel because of concern about a possible bioterror attack using smallpox.
See also inoculation.
See study by A. Allen (2007).
The word vaccination was first used by Edward Jenner in 1796. Louis Pasteur furthered the concept through his pioneering work in microbiology. Vaccination (Latin: vacca—cow) is so named because the first vaccine was derived from a virus affecting cows—the relatively benign cowpox virus—which provides a degree of immunity to smallpox, a contagious and deadly disease. In common speech, 'vaccination' and 'immunization' generally have the same colloquial meaning. This distinguishes it from inoculation which uses unweakened live pathogens, although in common usage either is used to refer to an immunization. The word "vaccination" was originally used specifically to describe the injection of smallpox vaccine.
Vaccination efforts have been met with some controversy since their inception, on ethical, political, medical safety, religious, and other grounds. Early success and compulsion brought widespread acceptance and mass vaccination campaigns were undertaken which are credited with greatly reducing the incidence of many diseases in numerous geographic regions.
In the generic sense, the process of artificial induction of immunity, in an effort to protect against infectious disease, works by 'priming' the immune system with an 'immunogen'. Stimulating immune response, via use of an infectious agent, is known as immunization. Vaccinations involve the administration of one or more immunogens, which can be administered in several forms.
Some modern vaccines are administered after the patient already has contracted a disease, as in the cases of experimental AIDS, cancer and Alzheimer's disease vaccines. Vaccinia given after exposure to smallpox, within the first four days, is reported to attenuate the disease considerably, and vaccination within the first week is known to be beneficial to a degree. The first rabies immunization was given by Louis Pasteur to a child bitten by a rabid dog, subsequently post-exposure immunization to rabies has generally been followed by survival. The essential empiricism behind such immunizations is that the vaccine triggers an immune response more rapidly than the natural infection itself.
Most vaccines are given by hypodermic injection as they are not absorbed reliably through the gut. Live attenuated polio, some typhoid and some cholera vaccines are given orally in order to produce immunity based in the bowel.
All vaccinations work by presenting a foreign antigen to the immune system in order to evoke an immune response, but there are several ways to do this. The three main types are as follows:
Early forms of vaccination were developed in ancient China as early as 200 B.C. Scholar Ole Lund comments: "The earliest documented examples of vaccination are from India and China in the 17th century, where vaccination with powdered scabs from people infected with smallpox was used to protect against the disease. Smallpox used to be a common disease throughout the world and 20% to 30% of infected persons died from the disease. Smallpox was responsible for 8 to 20% of all deaths in several European countries in the 18th century. The tradition of vaccination may have originated in India in AD 1000. The mention of vaccination in the Sact'eya Grantham, an Ayurvedic text, was noted by the French scholar Henri Marie Husson in the journal Dictionaire des sciences me`dicales. Almroth Wright, the professor of pathology at Netley, further helped shape the future of vaccination by conducting limited experiments on the professional staff at Netly, including himself. The outcome of these experiments resulted in further development of vaccination in Europe. The Anatolian Ottoman Turks knew about methods of vaccination about a hundred years before Edward Jenner to whom the discovery is attributed. They called vaccination Ashi or engrafting, which they used to apply to their children with cowpox taken from the breast of cattle. This kind of vaccination and other forms of variolation were introduced into England by Lady Montagu, a famous English letter-writer and wife of the English ambassador at Istanbul between 1716 and 1718. She came across the Turkish methods of vaccination, consenting to have her son inoculated by the Embassy surgeon Charles Maitland in the Turkish way. Lady Montagu wrote to her sister and friends in England describing the process in details. On her return to England she continued to propagate the Turkish tradition of vaccination and had many of her relatives inoculated. The breakthrough came when a scientific description of the vaccination operation was submitted to the Royal Society in 1724 by Dr Emmanual Timoni, who had been the Montagu’s family physician in Istanbul. Inoculation was adopted both in England and in France nearly half a century before Jenner's famous smallpox vaccine of 1796.
Since then vaccination campaigns have spread throughout the globe, sometimes prescribed by law or regulations (See Vaccination Acts). Vaccines are now used to fight a wide variety of disease threats besides smallpox. Louis Pasteur further developed the technique during the 19th century, extending its use to protecting against bacterial anthrax and viral rabies. The method Pasteur used entailed treating the infectious agents for those diseases so they lost the ability to cause serious disease. Pasteur adopted the name vaccine as a generic term in honor of Jenner's discovery, which Pasteur's work built upon.
Prior to vaccination with cowpox, the only known protection against smallpox was inoculation or variolation (Variola - the Smallpox viruses) where a small amount of live smallpox virus was administered to the patient; this carried the serious risk that the patient would be killed or seriously ill. The death rate from variolation was reported to be around a tenth of that from natural infection with Variola, and the immunity provided was considered quite reliable. Factors contributing to the efficacy of variolation probably include the choices of Variola Minor strains used, the relatively low number of cells infected in the first phase of multiplication following initial exposure, and the exposure route used, via the skin or nasal lining rather than inhalation of droplets into the lungs.
Consistency would suggest the activity should have predated Jenner's description of an effective vaccination system, and there is some history relating to opposition to the older and more hazardous procedure of variolation.
In modern times, the first vaccine-preventable disease targeted for eradication was smallpox. The World Health Organization (WHO) coordinated the global effort to eradicate this disease. The last naturally occurring case of smallpox occurred in Somalia in 1977.
In 1988, the governing body of WHO targeted polio for eradication by the year 2000. Although the target was missed, eradication is very close. The next eradication target would most likely be measles, which has declined since the introduction of measles vaccination in 1963.
In 2000, the Global Alliance for Vaccines and Immunization was established to strengthen routine vaccinations and introduce new and under-used vaccines in countries with a per capita GDP of under US$1000. GAVI is now entering its second phase of funding, which extends through 2014.
In an attempt to eliminate the risk of outbreaks of some diseases, at various times several governments and other institutions have instituted policies requiring vaccination for all people. For example, an 1853 law required universal vaccination against smallpox in England and Wales, with fines levied on people who did not comply. Common contemporary U.S. vaccination policies require that children receive common vaccinations before entering school. Most other countries also have some compulsory vaccinations.
Beginning with early vaccination in the nineteenth century, these policies led to resistance from a variety of groups, collectively called anti-vaccinationists, who objected on ethical, political, medical safety, religious, and other grounds. Common objections are that compulsory vaccination represents excessive government intervention in personal matters, or that the proposed vaccinations are not sufficiently safe. Many modern vaccination policies allow exemptions for people who have compromised immune systems, allergies to the components used in vaccinations or strongly-held objections.
Vaccines typically contain one or more adjuvants, used to boost the immune response. Tetanus toxoid, for instance, is usually adsorbed onto alum. This presents the antigen in such a way as to produce a greater action than the simple aqueous tetanus toxoid. People who get an excessive reaction to adsorbed tetanus toxoid may be given the simple vaccine when time for a booster occurs.
In the preparation for the 1990 Gulf campaign, Pertussis vaccine (not acellular) was used as an adjuvant for Anthrax vaccine. This produces a more rapid immune response than giving only the Anthrax, which is of some benefit if exposure might be imminent.
They may also contain preservatives, which are used to prevent contamination with bacteria or fungi. Until recent years, the preservative thiomersal was used in many vaccines that did not contain live virus. As of 2005, the only childhood vaccine in the U.S. that contains thiomersal in greater than trace amounts is the influenza vaccine , which is currently recommended only for children with certain risk factors. The UK is considering Influenza immunisation in children perhaps as soon as in 2006-7. Single-dose Influenza vaccines supplied in the UK do not list Thiomersal (its UK name) in the ingredients. Preservatives may be used at various stages of production of vaccines, and the most sophisticated methods of measurement might detect traces of them in the finished product, as they may in the environment and population as a whole
Combined vaccinations are now widely used around the world, a result of the rapid increase in the number of shots recommended in current vaccination schedules.
A vaccine administration may be oral, by injection (intramuscular, intradermal, subcutaneous), by puncture, transdermal or intranasal.