Immunization

Last updated
Dr. Schreiber of San Augustine giving a typhoid inoculation at a rural school, San Augustine County, Texas. Transfer from U.S. Office of War Information, 1944. Typhoid inoculation2.jpg
Dr. Schreiber of San Augustine giving a typhoid inoculation at a rural school, San Augustine County, Texas. Transfer from U.S. Office of War Information, 1944.

Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the immunogen). When this system is exposed to molecules that are foreign to the body, called non-self, it will orchestrate an immune response, and it will also develop the ability to quickly respond to a subsequent encounter because of immunological memory. This is a function of the adaptive immune system. Therefore, by exposing a human, or an animal, to an immunogen in a controlled way, its body can learn to protect itself: this is called active immunization. The most important elements of the immune system that are improved by immunization are the T cells, B cells, and the antibodies B cells produce. Memory B cells and memory T cells are responsible for a swift response to a second encounter with a foreign molecule. Passive immunization is direct introduction of these elements into the body, instead of production of these elements by the body itself.

Contents

Immunization happens in various ways, both in the wild and as done by human efforts in health care. Natural immunity is gained by those organisms whose immune systems succeed in fighting off a previous infection, if the relevant pathogen is one for which immunization is even possible. Natural immunity can have degrees of effectiveness (partial rather than absolute) and may fade over time (within months, years, or decades, depending on the pathogen). In health care, the main technique of artificial induction of immunity is vaccination, [1] which is a major form of prevention of disease, whether by prevention of infection (pathogen fails to mount sufficient reproduction in the host), prevention of severe disease (infection still happens but is not severe), or both. Vaccination against vaccine-preventable diseases is a major relief of disease burden even though it usually cannot eradicate a disease. Vaccines against microorganisms that cause diseases can prepare the body's immune system, thus helping to fight or prevent an infection. The fact that mutations can cause cancer cells to produce proteins or other molecules that are known to the body forms the theoretical basis for therapeutic cancer vaccines. Other molecules can be used for immunization as well, for example in experimental vaccines against nicotine (NicVAX) or the hormone ghrelin in experiments to create an obesity vaccine.

Immunizations are often widely stated as less risky and an easier way to become immune to a particular disease than risking a milder form of the disease itself. They are important for both adults and children in that they can protect us from the many diseases out there. Immunization not only protects children against deadly diseases but also helps in developing children's immune systems. [2] Through the use of immunizations, some infections and diseases have almost completely been eradicated throughout the World. One example is polio. Thanks to dedicated health care professionals and the parents of children who vaccinated on schedule, polio has been eliminated in the U.S. since 1979. Polio is still found in other parts of the world so certain people could still be at risk of getting it. This includes those people who have never had the vaccine, those who did not receive all doses of the vaccine, or those traveling to areas of the world where polio is still prevalent. Active immunization/vaccination has been named one of the "Ten Great Public Health Achievements in the 20th Century".

History

Before the introduction of vaccines, people could only become immune to an infectious disease by contracting the disease and surviving it. Smallpox (variola) was prevented in this way by inoculation, which produced a milder effect than the natural disease. The first clear reference to smallpox inoculation was made by the Chinese author Wan Quan (1499–1582) in his Douzhen xinfa (痘疹心法) published in 1549. [3] In China, powdered smallpox scabs were blown up the noses of the healthy. The patients would then develop a mild case of the disease and from then on were immune to it. The technique did have a 0.5–2.0% mortality rate, but that was considerably less than the 20–30% mortality rate of the disease itself. Two reports on the Chinese practice of inoculation were received by the Royal Society in London in 1700; one by Dr. Martin Lister who received a report by an employee of the East India Company stationed in China and another by Clopton Havers. [4] According to Voltaire (1742), the Turks derived their use of inoculation from neighbouring Circassia. Voltaire does not speculate on where the Circassians derived their technique from, though he reports that the Chinese have practiced it "these hundred years". [5] It was introduced into England from Turkey by Lady Mary Wortley Montagu in 1721 and used by Zabdiel Boylston in Boston the same year. In 1798 Edward Jenner introduced inoculation with cowpox (smallpox vaccine), a much safer procedure. This procedure, referred to as vaccination, gradually replaced smallpox inoculation, now called variolation to distinguish it from vaccination. Until the 1880s vaccine/vaccination referred only to smallpox, but Louis Pasteur developed immunization methods for chicken cholera and anthrax in animals and for human rabies, and suggested that the terms vaccine/vaccination should be extended to cover the new procedures. This can cause confusion if care is not taken to specify which vaccine is used e.g. measles vaccine or influenza vaccine.

Passive and active immunization

Medical student participating in a polio vaccine campaign in Mexico National Immunization Campaign in "San Miguel Topilejo".JPG
Medical student participating in a polio vaccine campaign in Mexico

Immunization can be achieved in an active or passive manner: vaccination is an active form of immunization.

Active immunization

A simplified diagram showing the process of immunization through the production of anti-bodies Simplified Immunization Diagram.jpg
A simplified diagram showing the process of immunization through the production of anti-bodies

Active immunization can occur naturally when a person comes in contact with, for example, a microbe. The immune system will eventually create antibodies and other defenses against the microbe. The next time, the immune response against this microbe can be very efficient; this is the case in many of the childhood infections that a person only contracts once, but then is immune.

Artificial active immunization is where the microbe, or parts of it, are injected into the person before they are able to take it in naturally. If whole microbes are used, they are pre-treated.

The importance of immunization is so great that the American Centers for Disease Control and Prevention has named it one of the "Ten Great Public Health Achievements in the 20th Century". [6] Live attenuated vaccines have decreased pathogenicity. Their effectiveness depends on the immune systems ability to replicate and elicits a response similar to natural infection. It is usually effective with a single dose. Examples of live, attenuated vaccines include measles, mumps, rubella, MMR, yellow fever, varicella, rotavirus, and influenza (LAIV).

Passive immunization

Passive immunization is where pre-synthesized elements of the immune system are transferred to a person so that the body does not need to produce these elements itself. Currently, antibodies can be used for passive immunization. This method of immunization begins to work very quickly, but it is short lasting, because the antibodies are naturally broken down, and if there are no B cells to produce more antibodies, they will disappear.

Passive immunization occurs physiologically, when antibodies are transferred from mother to fetus during pregnancy, to protect the fetus before and shortly after birth.

Artificial passive immunization is normally administered by injection and is used if there has been a recent outbreak of a particular disease or as an emergency treatment for toxicity, as in for tetanus. The antibodies can be produced in animals, called "serum therapy," although there is a high chance of anaphylactic shock because of immunity against animal serum itself. Thus, humanized antibodies produced in vitro by cell culture are used instead if available.

Economics of immunizations

If individuals make the decision to immunize based on the Private Marginal Benefit we see a quantity of Q1 at the price P1 while the socially optimal point is at quantity Q* and price P*. The distance between the private and marginal benefit lines is the cost of the marginal benefit to society. Immunization Externality.png
If individuals make the decision to immunize based on the Private Marginal Benefit we see a quantity of Q1 at the price P1 while the socially optimal point is at quantity Q* and price P*. The distance between the private and marginal benefit lines is the cost of the marginal benefit to society.
Immunization A does not have a social marginal benefit large enough to shift Q1 to Q(e), instead it lands at Q*. Non Eradicated Shift.png
Immunization A does not have a social marginal benefit large enough to shift Q1 to Q(e), instead it lands at Q*.

Positive externality

Immunizations impose what is known as a positive consumer externality on society. In addition to providing the individual with protection against certain antigens it adds greater protection to all other individuals in society through herd immunity. Because this extra protection is not accounted for in the market transactions for immunizations we see an undervaluing of the marginal benefit of each immunization. This market failure is caused by individuals making decisions based on their private marginal benefit instead of the social marginal benefit. Society's undervaluing of immunizations means that through normal market transactions we end up at a quantity that is lower than what is socially optimal. [7]

For example, if individual A values their own immunity to an antigen at $100 but the immunization costs $150, individual A will decide against receiving immunization. However, if the added benefit of herd immunity means person B values person A's immunity at $70 then the total social marginal benefit of their immunization is $170. Individual A's private marginal benefit being lower than the social marginal benefit leads to an under-consumption of immunizations.

Socially optimal outcome

Having private marginal benefits lower than social marginal benefits will always lead to an under-consumption of any good. The size of the disparity is determined by the value that society places on each different immunization. Many times, immunizations do not reach a socially optimum quantity high enough to eradicate the antigen. Instead, they reach a social quantity that allows for an optimal amount of sick individuals. Most of the commonly immunized diseases in the United States still see a small presence with occasional larger outbreaks. Measles is a good example of a disease whose social optimum leaves enough room for outbreaks in the United States that often lead to the deaths of a handful of individuals. [8]

Immunization B has a social marginal benefit large enough to bring Q1 to Q(e), the quantity at which eradication occurs. Eradicated Immunization Shift.png
Immunization B has a social marginal benefit large enough to bring Q1 to Q(e), the quantity at which eradication occurs.

There are also examples of illnesses so dangerous that the social optimum ended with the eradication of the virus, such as smallpox. In these cases, the social marginal benefit is so large that society is willing to pay the cost to reach a level of immunization that makes the spread and survival of the disease impossible.

Despite the severity of certain illnesses, the cost of immunization versus the social marginal benefit means that total eradication is not always the end goal of immunization. Though it is hard to tell exactly where the socially optimal outcome is, we know that it is not the eradication of all disease for which an immunization exists.

Internalizing the externality

In order to internalize the positive externality imposed by immunizations payments equal to the marginal benefit must be made. In countries like the United States these payment usually come in the form of subsidies from the government. Before 1962 immunization programs in the United States were run on the local and state level of governments. The inconsistency in subsidies lead to some regions of the United States reaching the socially optimal quantity while other regions were left without subsidies and remained at the private marginal benefit level of immunizations. Since 1962 and the Vaccination Assistance Act, the United States as a whole has been moving towards the socially optimal outcome on a larger scale. [9] Despite government subsidies it is difficult to tell when social optimum has been achieved. In addition to hardships determining the true social marginal benefit of immunizations we see cultural movements shifting private marginal benefit curves. Vaccine controversies have changed the way some private citizens view the marginal benefit of being immunized. If Individual A believes that there is a large health risk, possibly larger than the antigen itself, associated with immunization they will not be willing to pay for or receive immunization. With fewer willing participants and a widening marginal benefit reaching a social optimum becomes more difficult for governments to achieve through subsidies.

Outside of government intervention through subsidies, non profit organizations can also move a society towards the socially optimal outcome by providing free immunizations to developing regions. Without the ability to afford the immunizations to begin with, developing societies will not be able to reach a quantity determined by private marginal benefits. By running immunization programs organizations are able to move privately under-immunized communities towards the social optimum.

Race, ethnicity and immunization

In the United States, race and ethnicity are strong determinants of utilization of preventive and therapeutic health services as well as health outcomes. [10] Rates of infant mortality and most of the leading causes of overall mortality have been higher in African Americans than in European Americans. A recent analysis of mortality from influenza and pneumonia revealed that African Americans died of these causes at higher rates than European Americans in 1999–2018. [11] Contributing to these racial disparities are lower rates of immunization against influenza and pneumococcal pneumonia. [10] During the COVID-19 pandemic, death rates have been higher in African Americans than European Americans and vaccination rates have lagged in African Americans during the roll-out. [12] Among Hispanics immunization rates are lower than those in non-Hispanic whites. [13]

See also

Related Research Articles

<span class="mw-page-title-main">Polio</span> Infectious disease caused by poliovirus

Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 75% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe symptoms develop such as headache, neck stiffness, and paresthesia. These symptoms usually pass within one or two weeks. A less common symptom is permanent paralysis, and possible death in extreme cases. Years after recovery, post-polio syndrome may occur, with a slow development of muscle weakness similar to what the person had during the initial infection.

<span class="mw-page-title-main">Vaccination</span> Administration of a vaccine to protect against disease

Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating the body's adaptive immunity, they help prevent sickness from an infectious disease. When a sufficiently large percentage of a population has been vaccinated, herd immunity results. Herd immunity protects those who may be immunocompromised and cannot get a vaccine because even a weakened version would harm them. The effectiveness of vaccination has been widely studied and verified. Vaccination is the most effective method of preventing infectious diseases; widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the elimination of diseases such as polio and tetanus from much of the world. According to the World Health Organization (WHO), vaccination prevents 3.5–5 million deaths per year. A WHO-funded study by The Lancet estimates that, during the 50-year period starting in 1974, vaccination prevented 154 million deaths, including 146 million among children under age 5. However, some diseases have seen rising cases due to relatively low vaccination rates attributable partly to vaccine hesitancy.

<span class="mw-page-title-main">Vaccine</span> Pathogen-derived preparation that provides acquired immunity to an infectious disease

A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as a threat, destroy it, and recognize further and destroy any of the microorganisms associated with that agent that it may encounter in the future.

<span class="mw-page-title-main">Cowpox</span> Disease of humans and animals

Cowpox is an infectious disease caused by the cowpox virus (CPXV). It presents with large blisters in the skin, a fever and swollen glands, historically typically following contact with an infected cow, though in the last several decades more often from infected cats. The hands and face are most frequently affected and the spots are generally very painful.

<span class="mw-page-title-main">Herd immunity</span> Concept in epidemiology

Herd immunity is a form of indirect protection that applies only to contagious diseases. It occurs when a sufficient percentage of a population has become immune to an infection, whether through previous infections or vaccination, that the communicable pathogen cannot maintain itself in the population, its low incidence thereby reducing the likelihood of infection for individuals who lack immunity.

In biology, immunity is the state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease. Immunity may occur naturally or be produced by prior exposure or immunization.

<span class="mw-page-title-main">Influenza vaccine</span> Vaccine against influenza

Influenza vaccines, colloquially known as flu shots or the flu jab, are vaccines that protect against infection by influenza viruses. New versions of the vaccines are developed twice a year, as the influenza virus rapidly changes. While their effectiveness varies from year to year, most provide modest to high protection against influenza. Vaccination against influenza began in the 1930s, with large-scale availability in the United States beginning in 1945.

<span class="mw-page-title-main">Vaccine hesitancy</span> Reluctance or refusal to be vaccinated or have ones children vaccinated

Vaccine hesitancy is a delay in acceptance, or refusal, of vaccines despite the availability of vaccine services and supporting evidence. The term covers refusals to vaccinate, delaying vaccines, accepting vaccines but remaining uncertain about their use, or using certain vaccines but not others. Although adverse effects associated with vaccines are occasionally observed, the scientific consensus that vaccines are generally safe and effective is overwhelming. Vaccine hesitancy often results in disease outbreaks and deaths from vaccine-preventable diseases. Therefore, the World Health Organization characterizes vaccine hesitancy as one of the top ten global health threats.

Vaccination and religion have interrelations of varying kinds. No major religion prohibits vaccinations, and some consider it an obligation because of the potential to save lives. However, some people cite religious adherence as a basis for opting to forego vaccinating themselves or their children. Many such objections are pretextual: in Australia, anti-vaccinationists founded the Church of Conscious Living, a "fake church", leading to religious exemptions being removed in that country, and one US pastor was reported to offer vaccine exemptions in exchange for online membership of his church.

Artificial induction of immunity is immunization achieved by human efforts in preventive healthcare, as opposed to natural immunity as produced by organisms' immune systems. It makes people immune to specific diseases by means other than waiting for them to catch the disease. The purpose is to reduce the risk of death and suffering, that is, the disease burden, even when eradication of the disease is not possible. Vaccination is the chief type of such immunization, greatly reducing the burden of vaccine-preventable diseases.

In immunology, passive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin are transferred to non-immune persons through blood products that contain antibodies, such as in immunoglobulin therapy or antiserum therapy. Passive immunization is used when there is a high risk of infection and insufficient time for the body to develop its own immune response, or to reduce the symptoms of ongoing or immunosuppressive diseases. Passive immunization can be provided when people cannot synthesize antibodies, and when they have been exposed to a disease that they do not have immunity against.

<span class="mw-page-title-main">Immunization during pregnancy</span>

Immunization during pregnancy is the administration of a vaccine to a pregnant individual. This may be done either to protect the individual from disease or to induce an antibody response, such that the antibodies cross the placenta and provide passive immunity to the infant after birth. In many countries, including the US, Canada, UK, Australia and New Zealand, vaccination against influenza, COVID-19 and whooping cough is routinely offered during pregnancy.

An attenuated vaccine is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable. Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. These vaccines contrast to those produced by "killing" the pathogen.

A vaccination policy is a health policy adopted in order to prevent the spread of infectious disease. These policies are generally put into place by state or local governments, but may also be set by private facilities, such as workplaces or schools. Many policies have been developed and implemented since vaccines were first made widely available.

Mass vaccination is a public policy effort to vaccinate a large number of people, possibly the entire population of the world or of a country or region, within a short period of time. This policy may be directed during a pandemic, when there is a localized outbreak or scare of a disease for which a vaccine exists, or when a new vaccine is invented.

<span class="mw-page-title-main">Progressive vaccinia</span> Medical condition

Progressive vaccinia is a rare cutaneous condition caused by the vaccinia virus, characterized by painless but progressive necrosis and ulceration.

Vaccinia immune globulin (VIG) is made from the pooled blood of individuals who have been inoculated with the smallpox vaccine. The antibodies these individuals developed in response to the smallpox vaccine are removed and purified. This results in VIG. It can be administered intravenously. It is used to treat individuals who have developed progressive vaccinia after smallpox vaccination.

<span class="mw-page-title-main">Targeted immunization strategies</span>

Targeted immunization strategies are approaches designed to increase the immunization level of populations and decrease the chances of epidemic outbreaks. Though often in regards to use in healthcare practices and the administration of vaccines to prevent biological epidemic outbreaks, these strategies refer in general to immunization schemes in complex networks, biological, social or artificial in nature. Identification of at-risk groups and individuals with higher odds of spreading the disease often plays an important role in these strategies, since targeted immunization in high-risk groups is necessary for effective eradication efforts and has a higher return on investment than immunizing larger but lower-risk groups.

Inoculation is the act of implanting a pathogen or other microbe or virus into a person or other organism. It is a method of artificially inducing immunity against various infectious diseases. The term "inoculation" is also used more generally to refer to intentionally depositing microbes into any growth medium, as into a Petri dish used to culture the microbe, or into food ingredients for making cultured foods such as yoghurt and fermented beverages such as beer and wine. This article is primarily about the use of inoculation for producing immunity against infection. Inoculation has been used to eradicate smallpox and to markedly reduce other infectious diseases such as polio. Although the terms "inoculation", "vaccination", and "immunization" are often used interchangeably, there are important differences. Inoculation is the act of implanting a pathogen or microbe into a person or other recipient; vaccination is the act of implanting or giving someone a vaccine specifically; and immunization is the development of disease resistance that results from the immune system's response to a vaccine or natural infection.

<span class="mw-page-title-main">Non-specific effect of vaccines</span> Unintended side effects of vaccines which may be beneficial or bad

Non-specific effects of vaccines are effects which go beyond the specific protective effects against the targeted diseases. Non-specific effects from live vaccines can be strongly beneficial by increasing protection against non-targeted infections. This has been shown with two live attenuated vaccines, BCG vaccine and measles vaccine, through multiple randomized controlled trials. Non-specific effects of non-live vaccination may be detrimental, increasing overall mortality at least 30% by some estimates, despite providing protection against the target disease. Observational studies suggest that diphtheria-tetanus-pertussis vaccine (DTP) may be highly detrimental, and although a WHO report described such studies as at high risk of bias, the direction of such bias was not predicted; although the conclusions have failed to replicate in some similar studies conducted by independent groups, randomized controlled trials (RCTs) provide additional evidence that vaccines have potent nonspecific effects.

References

  1. ↑ "Vaccines". Archived from the original on 2020-11-14. Retrieved 2020-04-02.
  2. ↑ "Top Vaccination For Your Child". Vaxins. Archived from the original on 15 August 2016. Retrieved 29 July 2016.
  3. ↑ Needham, J. (1999). "Part 6, Medicine". Science and Civilization in China: Volume 6, Biology and Biological Technology. Cambridge: Cambridge University Press. p. 134.
  4. ↑ Silverstein, Arthur M. (2009). A History of Immunology (2nd ed.). Academic Press. p. 293. ISBN   9780080919461.
  5. ↑ Voltaire (1742). "Letter XI". Letters on the English. Archived from the original on 2018-10-16. Retrieved 2019-01-21.
  6. ↑ "Ten Great Public Health Achievements in the 20th Century". Archived 2016-03-13 at the Wayback Machine CDC
  7. ↑ Hinman, A. R.; Orenstein, W. A.; Rodewald, L. (2004-05-15). "Financing Immunizations in the United States". Clinical Infectious Diseases. 38 (10): 1440–1446. doi: 10.1086/420748 . ISSN   1058-4838. PMID   15156483.
  8. ↑ Cook, Joseph; Jeuland, Marc; Maskery, Brian; Lauria, Donald; Sur, Dipika; Clemens, John; Whittington, Dale (2009). "Using private demand studies to calculate socially optimal vaccine subsidies in developing countries". Journal of Policy Analysis and Management. 28 (1): 6–28. doi:10.1002/pam.20401. ISSN   0276-8739. PMID   19090047.
  9. ↑ "Vaccine-Preventable Diseases, Immunizations, and MMWR – 1961–2011". www.cdc.gov. Archived from the original on 2018-05-06. Retrieved 2018-03-07.
  10. 1 2 Health United States 2017 With special feature on mortality. Hyattsville, MD: National Center for Health Statistics. 2018.
  11. ↑ Donaldson, Sahai V.; Thomas, Alicia N.; Gillum, Richard F.; Mehari, Alem (January 2021). "Geographic Variation in Racial Disparities in Mortality From Influenza and Pneumonia in the United States in the Pre-Coronavirus Disease 2019 Era". Chest. 159 (6): 2183–2190. doi: 10.1016/j.chest.2020.12.029 . PMID   33400931.
  12. ↑ Bassett, Mary T.; Chen, Jarvis T.; Krieger, Nancy (20 October 2020). "Variation in racial/ethnic disparities in COVID-19 mortality by age in the United States: A cross-sectional study". PLOS Medicine. 17 (10): e1003402. doi: 10.1371/journal.pmed.1003402 . PMC   7575091 . PMID   33079941.
  13. ↑ Gorina, Y; Kelly, T; Lubitz, J; Hines, Z (2008). Trends in Influenza and Pneumonia Among Older Persons in the United States. Hyattsville, MD: National Center for Health Statistics.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.