51.   It is still too early to know whether it may be possible to develop an effective vaccine against obesity or otherwise counteract the effects of the virus.

52.   Meetings have addressed subjects from the development of an effective anti-AIDS vaccine to prevention of infection through protected sex.

53.   No effective vaccine is available.

54.   Researchers believe the most effective AIDS vaccine is likely to be a live virus, which will prime the body to mount a spirited reaction to HIV.

55.   Some researchers had hoped that a vaccine modeled on this weak virus could be an effective AIDS vaccine, protecting people for life without making them sick.

56.   The AIDS virus attacks the very parts of the immune system that are ordinarily called into action by effective vaccines.

57.   The government said there is no effective vaccine for the strain.

58.   They contend that in areas where the risk of catching HIV is extremely high, an effective vaccine would make sense even if does carry a slight risk.

59.   They use a highly effective oral vaccine made of live but weakened polio virus that protects not just individuals but society.

60.   With no effective AIDS vaccine close to development, the only way to stop the epidemic in these places is to keep people from getting infected.