The condition of active immunity to a disease agent resulting from the production of specific antibodies by the host, either after exposure to the disease or after vaccination. Immunization is generally synonymous with vaccination, although vaccination historically was immune protection against the variola virus by controlled infection with the related but generally safe cowpox virus.
Largely due to the early availability of active immunization for smallpox, that disease has been eradicated from the wild, and preventive immunization, which carries more risks than many other immune therapies, is no longer routinely recommended.
Immunizations in widespread use include:
Other immunizations, such as typhoid fever, cholera, yellow fever, and plague are recommended only for individuals who are at high risk, through travel, laboratory work with the organism, etc.
After immunization, active immunity takes time to develop. In acute disease such as tetanus, therapy requires both inducing passive immunity using antitoxin to neutralize circulating toxin. Antitoxin does not establish active immunity, so tetanus toxoid will be given to produce that type of immunity.