The Main Types of Vaccines

The safety and effectiveness of a vaccine depends on how it is made and what it contains. There are four main ways to develop vaccines:

• Live attenuated vaccines contain bacteria or viruses that have been altered so they can't cause disease.


• Killed vaccines contain killed bacteria or inactivated viruses.


• Toxoid vaccines contain toxins (or poisons) produced by the germ that have been made harmless.


• Component vaccines contain parts of the whole bacteria or viruses.

Live attenuated vaccines
Live attenuated vaccines usually are created from the naturally occurring germ itself. The germs used in these vaccines still can infect people, but they rarely cause serious disease. Viruses are weakened (or attenuated) by growing them over and over again in a laboratory under nourishing conditions called cell culture. The process of growing a virus repeatedly-also known as passing--serves to lessen the disease-causing ability of the virus. Vaccines are made from viruses whose disease-causing ability has deteriorated from multiple passages.

Examples of live attenuated vaccines include:

• Measles vaccine (as found in the MMR vaccine)
• Mumps vaccine (MMR vaccine)


• Rubella (German measles) vaccine ( MMR vaccine)


• Oral polio vaccine (OPV)


• Varicella (chickenpox) vaccine

Inactivated (killed) vaccines
Inactivated (killed) vaccines cannot cause an infection, but they still can stimulate a protective immune response. Viruses are inactivated with chemicals such as formaldehyde.

Examples of inactivated (killed) vaccines:

• Inactivated polio vaccine (IPV), which is the shot form of the polio vaccine


• Inactivated influenza vaccine

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