11.   As new anti-AIDS drugs lose their power against the quickly mutating virus, an effective vaccine could be the last, best hope to contain the epidemic.

12.   Because these chimpanzees apparently can live with the virus without falling ill, a hope is to use the discovery to eventually improve therapies and develop an effective vaccine.

13.   A banana vaccine effective against a combination of childhood diseases would also be welcome among millions of needle-shy American children and their parents.

14.   A report by the National Institutes of Health cautions that finding am effective AIDS vaccine is a tremendous undertaking.

15.   All but one of the industry researchers contended that an effective vaccine against the immunodeficiency virus HIV is achievable.

16.   But researchers say that in places like Botswana and South Africa, where infection rates are high, even a partly effective vaccine can make a big difference.

17.   Critics said it was unethical not to provide protection against the disease when an effective vaccine was available.

18.   Does the prospect of developing an effective AIDS vaccine justify condemning chimpanzees to death?

19.   Even assuming that a company could develop an AIDS vaccine effective against all strains, it still might add up to a poor investment.

20.   Few effective vaccines, even the one for hepatitis B, which was developed only after long testing in Senegal, have been made routinely available in Africa.