11. The vaccine is derived from a live virus whose disease-causing properties have been disabled. 12. This makes it difficult to tell a vaccinated animal from one harboring live virus . 13. The live virus vaccine promised lifetime immunity, while the original Salk vaccine did not. 14. Several vaccines are available that use modified live viruses . 15. Gonzalez, who cleaned up the spill, breathed in the live virus , Yale officials had said. 16. Many human vaccines are derived from weakened live viruses . 17. In contrast, inactivated virus vaccines contain no living virus , and cannot cause a live infection. 18. Because HIV is so unpredictable, vaccine researchers don't use the live virus in human experiments. 19. Many vaccines are made by weakening a live virus . 20. Both are taken orally and contain attenuated live virus .
