Inactivated vaccine

An inactivated vaccine (or killed vaccine) consists of virus particles, bacteria, or other pathogens 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 infectivity of the virus and prevent infection from the vaccine.

Because inactivated viruses tend to produce a weaker response by the immune system than live viruses, immunologic adjuvants and multiple "booster" injections may be required to provide an effective immune response against the inactivated pathogen.

Inactivated vaccines are further classified depending on the method used to inactivate the virus. Whole virus vaccines use the entire virus particle, fully destroyed using heat, chemicals,or radiation. Split virus vaccines are produced by using a detergent to disrupt the virus. Subunit vaccines are produced by purifying out the antigens that best stimulate the immune system to mount a response to the virus, while removing other components necessary for the virus to replicate or survive or that can cause adverse reactions.

Examples

Types include:

• viral: polio vaccine (Salk vaccine) and influenza vaccine
• bacterial: typhoid vaccine, cholera vaccine, plague vaccine, and pertussis vaccine

Inactivated vaccines are contrasted with a/an attenuated vaccines, or "live" vaccines.

Mechanism

The virus particles are destroyed and cannot replicate, but the virus capsid proteins maintain some of their integrity to be recognized by the immune system and evoke an adaptive immune response. When manufactured correctly, the vaccine is not infectious, but improper inactivation can result in intact and infectious particles. Because the killed pathogens in a properly produced vaccine do not reproduce, booster shots are required periodically to reinforce the immune response.