Vomiting is a physical release of "fear' energy in the Solar Plexus chakra. What story is he telling himself before these events? We feed our fears with our own thoughts... Am I afraid that I will mess up and be ridiculed? Am I afraid I will not be able to access my thoughts in order to convey pertinent information...therefore, "THIS" will happen to me? Over time, these stories/thoughts leave our conscious mind but our brain remembers the event and it only takes a split second for the fear to rise back up. Pinpoint the source...when did this feeling originate to find the answer..if not in this lifetime, karma brought in from another lifetime to be addressed and released.

For me, presentations bring up a time in my childhood where I got into trouble in school and was made to sit in front of the class. My nose began to bleed and the other children snickered or were grossed out. Now,as an adult, the story was long gone but the feeling of that remained ingrained into my conscious. Standing in front of people = NOT a pleasant experience and, therefore, should be avoided at all costs.
As far as interviews...attempting to speak as a child and being ridiculed or called stupid and, therefore, being an outcast was ingrained into my conscious. So, NOT knowing the interview questions, appearing stupid and not being 'wanted' by a company was always front and center during my interviews.

Identify the source and change the programming...Hypnosis and NLP should have identified and addressed the root cause, but was not stated in the question. GOOD LUCK!