A<unk>  is a biological preparation that provides active acquired immunity to a particular infectious disease. A<unk>  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 to further recognize and destroy any of the microorganisms associated with that agent that it may encounter in the future.<unk> s can be prophylactic (to prevent or ameliorate 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). Some<unk> s offer full sterilizing immunity, in which infection is prevented completely. The administration of<unk> s is called<unk> tion.<unk> tion is the most effective method of preventing infectious diseases; widespread immunity due to<unk> tion 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 effectiveness of<unk> tion has been widely studied and verified; for example,<unk> s that have proven effective include the influenza<unk> , the HPV<unk> , and the chickenpox<unk> . The World Health Organization (WHO) reports that licensed<unk> s are currently available for twenty-five different preventable infections. The terms<unk>  and<unk> tion are derived from Variolae<unk> e (smallpox of the cow), the term devised by Edward Jenner (who both developed the concept of<unk> s and created the first<unk>  to denote cowpox. He used the phrase in 1798 for the long title of his Inquiry into the Variolae<unk> e Known as the Cow Pox, in which he described the protective effect of cowpox against smallpox. In 1881, to honor Jenner, Louis Pasteur proposed that the terms should be extended to cover the new protective inoculations then being developed. The science of<unk>  development and production is termed<unk> logy. Infectious diseases before and after a<unk>  was introduced.<unk> tions have a direct effect on the diminishment of the number of cases and contributes indirectly to a diminishment of the number of deaths.
Vaccine
Animal vaccination
Vaccination
Therapeutic vaccines
Edible vaccines
Vaccination schedule
Booster dose
Cancer vaccine