Immunization
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
Immunization happens in various ways, both in the
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 (
Passive and active immunization
Immunization can be achieved in an active or passive manner: vaccination is an active form of immunization.
Active immunization
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
(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,
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
Economics of immunizations
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]
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
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
- Immunization registry
- Influenza vaccine
- Network theory
- Pandemic
- Targeted immunization strategies
- Vaccination
- Correlates of immunity
- Vaccine-preventable diseases
- World Immunization Week
References
- ^ "Vaccines". Archived from the original on 2020-11-14. Retrieved 2020-04-02.
- ^ "Top Vaccination For Your Child". Vaxins. Archived from the original on 15 August 2016. Retrieved 29 July 2016.
- ^ Needham, J. (1999). "Part 6, Medicine". Science and Civilization in China: Volume 6, Biology and Biological Technology. Cambridge: Cambridge University Press. p. 134.
- ISBN 9780080919461.
- ^ Voltaire (1742). "Letter XI". Letters on the English. Archived from the original on 2018-10-16. Retrieved 2019-01-21.
- ^ "Ten Great Public Health Achievements in the 20th Century". Archived 2016-03-13 at the Wayback Machine CDC
- PMID 15156483.
- PMID 19090047.
- ^ "Vaccine-Preventable Diseases, Immunizations, and MMWR – 1961–2011". www.cdc.gov. Archived from the original on 2018-05-06. Retrieved 2018-03-07.
- ^ a b Health United States 2017 With special feature on mortality. Hyattsville, MD: National Center for Health Statistics. 2018.
- PMID 33400931.
- PMID 33079941.
- ^ 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.
External links
- National Network for Immunization Information (NNii)
- Centers for Disease Control National Immunization Program
- Immunisation, BBC Radio 4 discussion with Nadja Durbach, Chris Dye & Sanjoy Bhattacharya (In Our Time, Apr. 20, 2006)