11.   Such a vaccine would have to generate killer T-cells, immune system warriors that recognize and destroy infected human cells.

12.   Targeted Genetics Corp., a Seattle-based biotech firm, is banking on such a vaccine.

13.   Such a vaccine would make it possible to differentiate between infected and vaccinated animals.

14.   The better such a vaccine is, the fewer times you use it.

15.   The MRC and the Gambian people are at the center of the international effort to develop such a vaccine.

16.   The potential market for such a vaccine is in the billions, said William Snow, a San Francisco advocate.

17.   There had been efforts to produce such a vaccine before the war, but some had caused paralysis instead of preventing it.

18.   While such a vaccine may not contain the epidemic, it would allow people to live longer with HIV, and reduce human suffering with the disease.

19.   But Zinkernagel said such a vaccine would not completely eliminate chances of infection.

20.   Every known strategy for making such a vaccine has been evaluated, but even the most promising candidate formulations to emerge are at best years from human use.