Sorry to say, but you are not safe from vertigo... although you are probably safe when it hits.
You probably experienced a bit of "mini-leans" at the beginning of the IMC training - the illusion of turning when in the climb, the illusion of flying straight and level in a prolonged turn etc. etc..
You then got over it by trusting the instruments, in particular the AI, and developing your scan. You probably barely notice it now.
When real vertigo hits you and you feel your head is spinning (in my case, over 100 hours after getting my IR) you have to go back to basics, do only the most fundamental scan (AI, turn coordinator, airspeed) to convince yourself that the aircraft is in control. Make sure that your AI actually works, though...
Reverting to straight and level helps, although that might not be an option depending the phase of flight. Just keep things nice and stable until vertigo subsides.
How much time in your training did you spend in actual IMC?