An inactivated vaccine consists of virus

Virus

A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

 particles which are grown in culture and then killed using a method such as heat or formaldehyde

Formaldehyde

Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

.

Examples

Types include:

• viral: polio vaccine
  Polio vaccine
  Two polio vaccines are used throughout the world to combat poliomyelitis . The first was developed by Jonas Salk and first tested in 1952. Announced to the world by Salk on April 12, 1955, it consists of an injected dose of inactivated poliovirus. An oral vaccine was developed by Albert Sabin...
  
   (Salk vaccine) and influenza vaccine
• bacterial: typhoid vaccine
  Typhoid vaccine
  Typhoid vaccine is a vaccine used against typhoid fever.There are two effective types:* Ty21a, which is a live vaccine* Vi capsular polysaccharide vaccine, which is a subunit vaccine...
  
  , cholera vaccine
  Cholera vaccine
  Cholera vaccine is a vaccine used against cholera.The first vaccines against cholera were developed in the late nineteenth century. These injected whole cell vaccine became increasingly popular until they were replaced by oral vaccines starting in the 1980s. Although no longer in use, the injected...
  
  , plague vaccine
  Plague vaccine
  Plague vaccine is a vaccine used against Yersinia pestis.-Plague immunization:A plague vaccine is used for an induction of active specific immunity in a susceptible organism to plague by means of administration an antigenic material via a variety of routes to people at risk of contracting any...
  
  , and pertussis vaccine
  Pertussis vaccine
  Pertussis vaccine is a vaccine used against Bordetella pertussis.It is a component of the DPT vaccine.Older versions of the vaccine involved inactivated cells. Newer versions are acellular, and are less likely to provoke a febrile state....
  
  

Inactivated vaccines are contrasted with Attenuated vaccines, or "live" vaccines. Examples of "live" (i.e. attenuated) vaccines include:

• Viral: measles vaccine
  Measles vaccine
  Measles vaccine is a highly effective vaccine used against measles. The measles-mumps-rubella-varicella combo vaccine has been available since 2005...
  
  , mumps vaccine
  Mumps vaccine
  Several varieties of mumps vaccine have been used since 1949, and at least 10 strains were in use in 2006:The first vaccine was a killed mumps virus vaccine developed in 1948 and used in the United States from 1950-1978. This vaccine produced little immune memory, thus had a short duration of...
  
  , rubella vaccine
  Rubella vaccine
  Rubella vaccine is a vaccine used against rubella.One form is called "Meruvax"....
  
  , chicken pox vaccine, yellow fever vaccine
  Yellow fever vaccine
  Yellow fever vaccine is a vaccine used against yellow fever.The vaccine consists of a live, but attenuated, strain of the yellow fever virus called 17D. The 17D vaccine has been used commercially since the 1950s. The mechanisms of attenuation and immunogenicity for the 17D strain are not known...
  
  , and nasal-spray flu vaccine (including the seasonal flu nasal spray and the 2009 H1N1 flu nasal spray). Rabies vaccine
  Rabies vaccine
  Rabies vaccine is a vaccine used to control rabies. Rabies can be prevented by vaccination, both in humans and other animals.-In animals:Currently, pre-exposure immunization has been used on domesticated and normal non-human populations...
  
  s are now available in two different attenuated forms, one for use in humans, and one for animal usage.
• Bacterial: BCG vaccine, typhoid vaccine
  Typhoid vaccine
  Typhoid vaccine is a vaccine used against typhoid fever.There are two effective types:* Ty21a, which is a live vaccine* Vi capsular polysaccharide vaccine, which is a subunit vaccine...
  
  

Mechanism

The virus particles are destroyed and cannot replicate, but the virus capsid

Capsid

A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...

 proteins are intact enough to be recognized by the immune system and evoke a response. When manufactured correctly, the vaccine is not infectious, but improper inactivation can result in intact and infectious particles. Since the properly produced vaccine does not reproduce, booster

Booster dose

In medicine, a booster dose is an extra administration of a vaccine after an earlier dose. After initial immunization, a booster injection or booster dose is a re-exposure to the immunizing antigen. It is intended to increase immunity against that antigen back to protective levels after it has been...

shots are required periodically to reinforce the immune response.