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- DictionaryVac·cine/vakˈsēn/
noun
- 1. a substance used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease: "every year the flu vaccine is modified to deal with new strains of the virus"
Apr 23, 2024 · 23 April 2024 | Q&A. What is vaccination? How does a vaccine work? When should I get vaccinated (or vaccinate my child)? Why should I get vaccinated? What diseases do vaccines prevent? Who can get vaccinated? What is in a vaccine? Are vaccines safe?
- Vaccines and Immunization
When you get a vaccine, your immune system responds. We now...
- MMR Vaccines and Autism
Concerns about a possible link between vaccination with MMR...
- How Do Vaccines Work
Once the antigen-specific antibodies are produced, they work...
- Vaccines and Immunization
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.
- Overview
- The first vaccines
- Vaccine effectiveness
- Vaccine types
- Table of vaccine-preventable diseases
A vaccine is a suspension of weakened, killed, or fragmented microorganisms or toxins or other biological preparation, such as those consisting of antibodies, lymphocytes, or mRNA, that is administered primarily to prevent disease.
How are vaccines made?
A vaccine is made by first generating the antigen that will induce a desired immune response. The antigen can take various forms, such as an inactivated virus or bacterium, an isolated subunit of the infectious agent, or a recombinant protein made from the agent. The antigen is then isolated and purified, and substances are added to it to enhance activity and ensure stable shelf life. The final vaccine is manufactured in large quantities and packaged for widespread distribution. Learn more about mRNA vaccine creation.
What is a vaccine delivery system?
A vaccine delivery system is the means by which the immune-stimulating agent constituting the vaccine is packaged and administered into the human body to ensure that the vaccine reaches the desired tissue. Examples of vaccine delivery systems include liposomes, emulsions, and microparticles.
How do vaccines work?
The first vaccine was introduced by British physician Edward Jenner, who in 1796 used the cowpox virus (vaccinia) to confer protection against smallpox, a related virus, in humans. Prior to that use, however, the principle of vaccination was applied by Asian physicians who gave children dried crusts from the lesions of people suffering from smallpo...
After Pasteur’s time, a widespread and intensive search for new vaccines was conducted, and vaccines against both bacteria and viruses were produced, as well as vaccines against venoms and other toxins. Through vaccination, smallpox was eradicated worldwide by 1980, and polio cases declined by 99 percent. Other examples of diseases for which vaccines have been developed include mumps, measles, typhoid fever, cholera, plague, tuberculosis, tularemia, pneumococcal infection, tetanus, influenza, yellow fever, hepatitis A, hepatitis B, some types of encephalitis, and typhus—although some of those vaccines are less than 100 percent effective or are used only in populations at high risk. Vaccines against viruses provide especially important immune protection, since, unlike bacterial infections, viral infections do not respond to antibiotics.
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The challenge in vaccine development consists in devising a vaccine strong enough to ward off infection without making the individual seriously ill. To that end, researchers have devised different types of vaccines. Weakened, or attenuated, vaccines consist of microorganisms that have lost the ability to cause serious illness but retain the ability to stimulate immunity. They may produce a mild or subclinical form of the disease. Attenuated vaccines include those for measles, mumps, polio (the Sabin vaccine), rubella, and tuberculosis. Inactivated vaccines are those that contain organisms that have been killed or inactivated with heat or chemicals. Inactivated vaccines elicit an immune response, but the response often is less complete than with attenuated vaccines. Because inactivated vaccines are not as effective at fighting infection as those made from attenuated microorganisms, greater quantities of inactivated vaccines are administered. Vaccines against rabies, polio (the Salk vaccine), some forms of influenza, and cholera are made from inactivated microorganisms. Another type of vaccine is a subunit vaccine, which is made from proteins found on the surface of infectious agents. Vaccines for influenza and hepatitis B are of that type. When toxins, the metabolic by-products of infectious organisms, are inactivated to form toxoids, they can be used to stimulate immunity against tetanus, diphtheria, and whooping cough (pertussis).
In the late 20th century, advances in laboratory techniques allowed approaches to vaccine development to be refined. Medical researchers could identify the genes of a pathogen (disease-causing microorganism) that encode the protein or proteins that stimulate the immune response to that organism. That allowed the immunity-stimulating proteins (called antigens) to be mass-produced and used in vaccines. It also made it possible to alter pathogens genetically and produce weakened strains of viruses. In that way, harmful proteins from pathogens can be deleted or modified, thus providing a safer and more-effective method by which to manufacture attenuated vaccines.
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Recombinant DNA technology has also proven useful in developing vaccines to viruses that cannot be grown successfully or that are inherently dangerous. Genetic material that codes for a desired antigen is inserted into the attenuated form of a large virus, such as the vaccinia virus, which carries the foreign genes “piggyback.” The altered virus is injected into an individual to stimulate antibody production to the foreign proteins and thus confer immunity. The approach potentially enables the vaccinia virus to function as a live vaccine against several diseases, once it has received genes derived from the relevant disease-causing microorganisms. A similar procedure can be followed using a modified bacterium, such as Salmonella typhimurium, as the carrier of a foreign gene.
Vaccines against human papillomavirus (HPV) are made from viruslike particles (VLPs), which are prepared via recombinant technology. The vaccines do not contain live HPV biological or genetic material and therefore are incapable of causing infection. Two types of HPV vaccines have been developed, including a bivalent HPV vaccine, made using VLPs of HPV types 16 and 18, and a tetravalent vaccine, made with VLPs of HPV types 6, 11, 16, and 18.
Vaccine-preventable diseases in the United States, presented by year of vaccine development or licensure.
Jul 21, 2020 · Vaccines are products that prepare the immune system to detect and eradicate certain disease-causing pathogens. Ultimately, vaccines help reduce the devastating impact of preventable diseases.
May 24, 2023 · Vaccines work by imitating an infection —the presence of a disease-causing organism in the body—to engage the body’s natural defenses. The active ingredient in all vaccines is an antigen, the name for any substance that causes the immune system to begin producing antibodies. In a vaccine, the antigen could be either.
Feb 22, 2022 · What are vaccines? Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs. For example, there are vaccines to protect against diseases caused by: Viruses, like the ones that cause the flu and COVID-19.
