Sort of. The tyrant virus constantly mutates, all "cures" are in the form of vaccines. This only teaches the body how to protect itself from a virus of the same design as the vaccine. As it mutates, a new vaccine is needed. This is why Flu drugs must be created from scratch each year.
That isn't necessarily true. The T-virus doesn't always mutate. The Gene virus is what causes the creature to mutate, and it will continuously.
A vaccine simply tells the body how to fight a specific vector and speeds its reaction time. There are some treatments that give you straight antibodies rather then teach your body how to fight, but they won't help your body learn. The latter is the only type that works during an actual infection.
In the games, it is portrayed as functioning slightly differently:
Even when they do work, they don't totally destroy the virus; they enable the body to fight it, but the virus always remains in the body along with the antibodies.