(Capcom's primary storyline)
The G-Vaccine was a supposed experimental vaccine engineered by WilPharma in 2005.
According to WilPharma's Chief of Research, Frederic Downing, he and Senator Ron Davis colluded with one another to obtain a G-Virus sample through the bioweapons black market. Davis believed it was in order to have a vaccine ready as soon as possible without waiting for the US government to sanction their research. In reality this was all part of Frederic's plan to advertise the lethality of both the G- and t-Viruses to General Miguel Grandé, with Davis' knowledge being falsified as a means of diverting attention away from him after faking his death.