A trauma symbiote is a piece of living spellware that can absorb damage, thus saving your miserable skin. It has five wound points, and will take damage off these wound points before any damage is applied to you. The attack that brings the symbiote past its wound treashold is always fully absorbed, but after taking this damage, the Symbiote must make a DeathTest, comparing the excess damage to its wound point rating. If it fails this test, it needs to be replaced (which usually happens by the next session).
Unless it has failed a death thest, any healing applied to you beyond that required to negate al your Wound Points is applied to the symbiote.
It is possible to bye this schtick several times; each additional time after the first adds another five wound points of absorption.