Immunization

A child being immunized against polio.

Immunization (or immunisation in British English) is the process of conferring increased resistance to an infectious disease by a means other than experiencing the natural infection. Typically, this involves exposure to an agent (antigen or immunogen) that is designed to fortify the person's immune system against that agent or similar infectious agents (active immunization). Immunization also can include providing the subject with protective antibodies developed by someone else (passive immunization).

When the human immune system is exposed to a disease once, it can develop the ability to quickly respond to a subsequent infection. Therefore, by exposing an individual to an immunogen in a controlled way, the person's body will then be able to protect itself from infection later on in life.

The term immunization often is used interchangeably with vaccination and inoculation, all of which use a viable infecting agent. Like active immunization, vaccination involves administration of antigenic material to produce immunity to a disease, which will prevent or ameliorate the effects of infection by a pathogen. This material can either be live, but weakened forms of pathogens (such as bacteria or viruses); killed or inactivated forms of these pathogens; or purified material such as proteins. While vaccination is used today in the same sense as immunization, in a strict sense the term refers to its original meaning, which is protection conferred against smallpox by material taken from cow infected with Cowpox virus, which is related to the vaccinia virus (Blakemore and Jennett 2001). While in common use the term inoculation can be used synonymously for immunization, it is often limited to a process involving unweakened, live pathogens. The term inoculation is used less frequently nowadays (Blakemore and Jennett 2001).

History of immunization

Recognizing that an infectious disease, once overcome, did not normally reappear, people have tried to prevent getting a disease by purposely inoculating themselves with infected material. This is first known with smallpox (NMAH 2007) before 200 B.C.E. (NMAH 2007).

In 1718, Lady Mary Wortley Montague reported that the Turks have a habit of deliberately inoculating themselves with fluid taken from mild cases of smallpox and she inoculated her own children (Behbehani 1983). In 1796 Edward Jenner inoculated using cowpox (a mild relative of the deadly smallpox virus).

While Dr. Edward Jenner (1749-1823) has been recognized as the first doctor to give sophisticated immunization, it was British dairy farmer Benjamin Jestey who noticed that "milkmaids" did not become infected with smallpox, or displayed a milder form. Jestey took the pus from an infected cow's udder and inoculated his wife and children with cowpox, in order to artificially induce immunity to smallpox during the epidemic of 1774, thereby making them immune to smallpox.

By injecting a human with the cowpox virus (which was harmless to humans), Jenner swiftly found that the immunized human was then also immune to smallpox. The process spread quickly, and the use of cowpox immunization has led to the almost total eradication of smallpox in modern human society. After successful vaccination campaigns throughout the 19th and 20th centuries, the World Health Organization (WHO) certified the eradication of smallpox in 1979.

Passive and active immunization

Passive immunization

Passive immunization is where pre-made antibodies, developed by someone else, are given to a person. This may involve administration of immune globulin from one individual organism to another or through the natural transfer of antibodies developed by a mother across the placental during pregnancy to the infant, helping to protect the child before and shortly after birth (Breslow 2002). In the former, the antibodies are normally produced in animals and injected into humans.

This method of immunization begins to work very quickly, but it is temporary and generally short lasting, because the antibodies are naturally broken down, and not stored for later use. It can also result in serum sickness and anaphylaxis.

Artificial passive immunization is normally given by injection and is used if there has been a recent outbreak of a particular disease or as an emergency treatment to poisons from insects, and so forth.

Active immunization

Active immunization involves the administration of an antigenic substance into a person, such as the actual infectious microbe, and then the development of antibodies by the recipient. Normally, this protection last for years or even confers lifetime immunity (Breslow 20020.

Active immunization can occur naturally when an untreated microbe is received by a person who has not yet come into contact with the microbe and has no pre-made antibodies for defense. The immune system will eventually create antibodies for the microbe, but this is a slow process and, if the microbe is deadly, there may not be enough time for the antibodies to begin being used.

Artificial active immunization is where the microbe is injected into the person before they are able to take it in naturally. The microbe is treated, so that it will not harm the injected person. Depending on the type of disease, this technique also works with dead microbes, parts of the microbe, or treated toxins from the microbe.

Required immunizations upon entry to school

In the USA each state provides school districts with an obligation to regulate those eligible to enter public schooling. Since schools are congregate settings, and thus communication of diseases is a consideration, school districts may exclude children who seek to attend without the protection of certain immunizations.

For example, in the state of Ohio, USA, each student is required to provide proof of specific immunizations or have an authorized waiver from the requirement upon entry to school at age 6 years. If a student does not have the necessary immunizations or a waiver acceptable to the state, the school principal may refuse entry and require compliance with a set deadline. This procedure is for the safety of all students and follows Ohio State law.

Unless given a waiver, students must meet the following requirements:

1. DPT (Diphtheria, pertussis, tetanus)—Five doses if the fourth one was before the fourth birthday.
2. Measles—Two doses, the first one after 12 months of age, and the second at least 28 days after the first birthday.
3. Rubella—Same as measles.
4. Mumps—Same as measles.
5. Polio—Four doses if the third was before the fourth birthday.
6. Hepatitis B—For students starting kindergarten.

Additionally, for schools offering a pre-school program, add the requirements for two doses of haemophilus influenzae.

References

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Blakemore

Breslow

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External Links

• National Network for Immunization Information (NNii)
• Centers for Disease Control National Immunization Program

Vaccination/Vaccine (and Immunization, Inoculation. See also List of vaccine topics and Epidemiology)

Development: Models - Timeline - Toxoid - Trial Administration: ACIP - GAVI - VAERS - Vaccination schedule - VSD Specific vaccines: Anthrax - BCG - Cancer - DPT - Flu - HIV - HPV - MMR - Pneumonia - Polio - Smallpox Controversy: A-CHAMP - Anti-vaccinationists - NCVIA - Pox party - Safe Minds - Simpsonwood - Thimerosal controversy - Vaccine injury

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