Attenuated. A disease-causing virus or bacterium that is weakened in a laboratory so it cannot cause disease. Live attenuated viruses are often used as vaccines because, although weakened, they can stimulate a strong immune response.

What does it mean if a vaccine is attenuated?

Live attenuated vaccines contain whole bacteria or viruses which have been “weakened”(attenuated) so that they create a protective immune response but do not cause disease in healthy people.

What are examples of live attenuated vaccines?

• Measles, mumps, rubella (MMR combined vaccine)
• Rotavirus.
• Smallpox.
• Chickenpox.
• Yellow fever.