I would like to add an important revelation that RE3 introduced to the series. The existence of an antidote (vaccine) for the T-Virus. Sure RE2 had one, but it was for the G-virus. Until RE3 it was never mentioned, and wasn't until Degeneration. The formula for the T-Virus was lost when Raccoon City was wiped out, and Wilpharma had to start over from scratch.