If it's the vapor barrier, you should use 3M window weld roll...not the caulk...not silicone or tape.
Jake was talking about the rubber door gasket, not the vapor barrier.
Window weld is the same as is used to seal the VB. If it's torn, tape it up (gorilla tape is good). If it's unsealed around its perimeter, then use window weld. (Available at an auto body supply shop...call up local auto body shop and ask where they get their supplies).