The flu vaccine is an excellent example of modern vaccination. Due to the evolution of the influenza virus, new influenza vaccines are created each year. According to the [http://www.cdc.gov/ CDC] <ref>"Inactivated Influenza Vaccine, What you need to know," a publication of the Center for Disease Control, 2006. Available online at: http://www.cdc.gov/nip/publications/VIS/vis-flu.pdf</ref>, | The flu vaccine is an excellent example of modern vaccination. Due to the evolution of the influenza virus, new influenza vaccines are created each year. According to the [http://www.cdc.gov/ CDC] <ref>"Inactivated Influenza Vaccine, What you need to know," a publication of the Center for Disease Control, 2006. Available online at: http://www.cdc.gov/nip/publications/VIS/vis-flu.pdf</ref>, |