Entity-specific Damage Invulnerability

Damage type invulnerability for an entity can be set with the following command:

/dmginvuln <entities> set <damage_type> <invulnerable>

/dmginvuln @a set fall true - sets fall damage immunity for all players

You can query damage type invulnerability with:

/dmginvuln <entities> get <damage_type>

/dmginvuln @e[type=creeper,limit=1, sort=nearest] get onFire - gets whether the closest creeper is invulnerable to fire or not