A attenuated vaccine is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable (or live). Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. These vaccines contrast to those produced by killing the virus (inactivated vaccine).xamples of live (example attenuated) vaccines include: 1  Viral: measles vaccine, mumps vaccine, rubella vaccine, Live attenuated influenza vaccine (the seasonal flu nasal spray and the 2009 H1N1 flu nasal spray), chicken pox vaccine, oral polio vaccine (Sabin), rotavirus vaccine, and yellow fever vaccine.