31.   Scientists now believe that the secret to an effective HIV vaccine lies in stimulating both arms of the immune system.

32.   That type of creative tinkering in the immune system is what is most likely to pay off in an effective vaccine, Greenberg said.

33.   The apparent purpose was to create a vaccine effective against a natural anthrax strain that produced these toxins.

34.   The flu is caused by a smaller family of viruses, which led to the development of an effective vaccine.

35.   The government should intensify its collaboration with the pharmaceutical and biotechnology industries to develop new classes of drugs and effective vaccines, the report said.

36.   The message in the latest U.N. estimates is that efforts to secure an effective vaccine must be broadened and greatly intensified.

37.   The information could be key to developing an effective vaccine, which is essential to stopping transmission.

38.   The only sensible response is better prevention programs and, most important of all, an effective vaccine to protect against infection.

39.   The virulent HIV strains are more aggressive than the strains that usually infect people, he says, so potentially effective vaccines could get overlooked.