why wasn't dr Karen in blade 2? because at the end of blade she said i'm gonna have to make more serum and thats its.

She probably took a step back from "active duty" to work on that serum, because apparently Blade does have a better one on that movie.

Also, Blade just lost his father figure and the one who developed all his tech. Feeling that Karen would be of more help if she stayed out of harm, Blade took a solitary path until taking Scout under his wing to develop more tech.

In my opinion, it makes even less sense that Karen is not in Blade Trinity as the lead developer of Ryan Reynolds' team. If she was the one to develop the new inhalator it would also connect with the flashback scene of Whistler explaining his story, which is taken from the first movie and apparently he was talking to both Karen and Abby.

Despite this long post, I never truly asked myself these questions because movies are movies xD. But I'm glad I can work out such a theory in the span of a few minutes, clearly says how much I love the Blade trilogy.

ok thanks