(Capcom's primary storyline)
It was administered to him regularly by Excella Gionne. The dosage given must be extremely precise and taken at certain times, otherwise it can act as a poison.
During Chapter 6-3, Jill instructs Chris and Sheva (in a cutscene) to inject the serum into Albert Wesker so that it should act "like a poison". During the second fight with Wesker in the Hangar, the player's mission is to inject the serum on him, causing an overdose.
- The "A/W" itself may suggest that it was specifically developed for Wesker.
- It is unknown if Alex Wesker had a similar serum or used one at all, though It's unlikely as she did not gain any powers from the Prototype Virus.