An inactivated vaccine (or killed vaccine) consists of virus particles which are grown in culture and then killed using a method such as heat or formaldehyde. These viruses are grown under controlled conditions and are rendered non-infectious as a means to reduce antigenicity. Large doses, adjuvants, and multiple doses are required to confer immunity.
- viral: polio vaccine (Salk vaccine) and influenza vaccine
- bacterial: typhoid vaccine, cholera vaccine, plague vaccine, and pertussis vaccine
Inactivated vaccines are contrasted with attenuated vaccines, or "live" vaccines.
The virus particles are destroyed and cannot replicate, but the virus capsid 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. Because the properly produced vaccine does not reproduce, booster shots are required periodically to reinforce the immune response.
- "Immunization". Retrieved 2009-03-10.