31.   But after that, polio would still exist in the children who received the oral vaccine, a relatively safe version of the live virus.

32.   Gonzalez, who cleaned up the spill, breathed in the live virus, Yale officials had said.

33.   It is made from a weakened live virus.

34.   Kawaoka said the technique will allow researchers to manipulate the plasmids in order to create live viruses that could be used for flu vaccines.

35.   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.

36.   The only known stocks of the live virus are contained in two secure laboratories in the United States and Russia.

37.   The vaccine is not made from live virus and therefore cannot cause infection.

38.   Yet the vaccine supply is fragile, depending on only four major vaccine manufacturers using live viruses and bacteria that can grow unpredictably.

39.   Varivax is made from the live virus that causes chickenpox, called varicella, but weakened enough to trigger immunity without causing disease.

40.   The only known samples of live virus are kept under tight security at laboratories in the United States and Russia.