Vaccine "Metroid"

The Metroid vaccine was a vaccine that saved Samus from death in Metroid Fusion. Once the X Parasite had infested Samus's central nervous system, she lost consciousness, causing her gunship to drift into an asteroid belt. Her ship's emergency systems automatically ejected the escape pod before impact, which Biologic Space Laboratories later retreived and transported Samus to Galactic Federation HQ. During the journey, the X multiplied within her, corrupting large areas of her Power Suit. It was learned that the organic components of her Power Suit had become so integrated with her central nervous system that it could not be removed while she was unconscious. Large portions of her suit had to be surgically removed, greatly altering her physical appearance. Unfortunately, the X in her central nervous system were too embedded to be removed safely, causing her to be given a minimal chance of survival. However, a cure was soon proposed. Doctors proposed using a Metroid cell to make an anti-X vaccine. This cell came from the infant Metroid that Samus found on SR388 and gave to Ceres Space Colony. The vaccine was injected and the X were immediately destroyed, causing the infant Metroid to save Samus's life a second time. However later in the game she realises that she is a easier target to the SA-X because the SA-X has an Ice Beam and Metroid are extremely sensitive to ice and since she is injected with Metroid she now has metroid-like traits. E.g her new fusion suit left arm has a claw like end, vaguely looking like a Metroid fang. After being given the vaccine doctors hypothesise that X were the natural prey to the Metroids which is why the treatment worked so well.