No one is immune. If anyone thinks they are, they're headed for hard times or disaster.
We had an independent multi-agency CISD/Peer Support team. While the members came from various LE, fire, EMS agencies, the agencies themselves had zero control of the team and confidentiality was absolute. Debriefings and support were always done by members of the team that were not from your agency, so I never debriefed anyone from my agency. Also, you only talked to someone from your profession: cop to cop, FF to FF, medic to medic.
Wayne Dobbs is absolutely right. If you need it, get help. Get outside your agency if you have to, but get it.