Goofs

A major plot point of Series 2 is that the scientists must reinfect Abby with the virus in order to extract her blood and make a cure. They even go so far as to say they don't know how her body will react as she is the only person to ever be infected twice. A person cannot be reinfected with an identical strain to a virus their body has already fought off once, because your body has developed antibodies to it. See more