The document discusses the sterility testing of vaccines. Sterility is a strict requirement for injectable drugs like vaccines. Sterility testing involves transferring vaccine samples to growth media and incubating for 14 days to check for microbial growth. If no growth is observed, a second round of incubation is done by transferring media contents to fresh media for 5-7 more days. There must be positive and negative controls, and no growth should be seen in the vaccine samples for the vaccine to pass sterility testing. The entire test takes 19-21 days to complete under aseptic conditions.