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A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease.

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 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. Vaccines can be prophylactic (to prevent or alleviate the effects of a future infection by a natural or "wild" pathogen), or therapeutic (to fight a disease that has already occurred, such as cancer). 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 restriction of diseases such as polio, measles, and tetanus from much of the world. The World Health Organization (WHO) reports that licensed vaccines are available for twenty-five different preventable infections. The first recorded use of inoculation to prevent smallpox (see variolation) occurred in the 16th century in China, with the earliest hints of the practice in China coming during the 10th century. It was also the first disease for which a vaccine was produced. The terms vaccine and vaccination are derived from Variolae vaccinae (smallpox of the cow), the term devised by Edward Jenner (who both developed the concept of vaccines and created the first vaccine) to denote cowpox. The science of vaccine development and production is termed vaccinology.

the strain of vaccine (some vaccines are specific to, or at least most effective against, particular strains of the disease)

The United States' program is known as the National Childhood Vaccine Injury Act, and the United Kingdom employs the Vaccine Damage Payment.

Examples include IPV (polio vaccine), hepatitis A vaccine, rabies vaccine and most influenza vaccines.

Rather than introducing an inactivated or attenuated microorganism to an immune system (which would constitute a "whole-agent" vaccine), a subunit vaccine uses a fragment of it to create an immune response.

An mRNA vaccine (or RNA vaccine) is a novel type of vaccine which is composed of the nucleic acid RNA, packaged within a vector such as lipid nanoparticles. For example, the Pfizer-BioNTech vaccine and Moderna mRNA vaccine are approved for use in adults and children in the US.

A DNA vaccine uses a DNA plasmid (pDNA)) that encodes for an antigenic protein originating from the pathogen upon which the vaccine will be targeted. pDNA is inexpensive, stable, and relatively safe, making it an excellent option for vaccine delivery.

This phenomenon was noted in the trivalent Sabin polio vaccine, where the relative amount of serotype 2 virus in the vaccine had to be reduced to stop it from interfering with the "take" of the serotype 1 and 3 viruses in the vaccine.

Adjuvants are added to promote an earlier, more potent response, and more persistent immune response to the vaccine; they allow for a lower vaccine dosage. Egg protein is present in the influenza vaccine and yellow fever vaccine as they are prepared using chicken eggs.

Another list of established vaccine abbreviations is at the CDC's page called "Vaccine Acronyms and Abbreviations", with abbreviations used on U.S. immunization records.

Until a vaccine is in use amongst the general population, all potential adverse events from the vaccine may not be known, requiring manufacturers to conduct Phase IV studies for postmarketing surveillance of the vaccine while it is used widely in the public. The FDA relies on a Vaccine Adverse Event Reporting System to monitor safety concerns about a vaccine throughout its use in the American public.

Eggs were used for virus propagation in the development of a yellow fever vaccine in 1935 and an influenza vaccine in 1945.

Quick Facts

• It was also the first disease for which a vaccine was produced.
• The terms vaccine and vaccination are derived from Variolae vaccinae (smallpox of the cow), the term devised by Edward Jenner (who both developed the concept of vaccines and created the first vaccine) to denote cowpox.
• Examples include IPV (polio vaccine), hepatitis A vaccine, rabies vaccine and most influenza vaccines.
• The science of vaccine development and production is termed vaccinology.
• 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.

Source material: Wikipedia - "Vaccine". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.