Synthetic antigen
From Memory Alpha, the free Star Trek reference.
A synthetic antigen is a manufactured anti-viral agent created from a living sample of the organism it is intended to destroy.
The Doctor created a synthetic antigen to combat an infection of the macrovirus encountered by the USS Voyager in 2373. The virus spread before the Doctor could innoculate the entire crew and eventually had to be dispersed by explosives. (VOY: "Macrocosm")
