Upon being released, Lucy Bauer infected Chen and later Melinda May. They suffered from a lethal disease which made them see other people with demonic faces, keeping them in a state of constant terror. Eventually, Chen died because of the disease and May almost did but was saved by Jemma Simmons and Holden Radcliffe. While curing May, Simmons and Radcliffe scanned her brain, which enabled them to understand the mechanism of the infection.
Simmons and Leo Fitz used the data of May's brain scan to create the antidote as a means to fight against Bauer and her fellow scientists. They managed to create it in time before S.H.I.E.L.D. went to the South Ridge Penitentiary to rescue Phil Coulson and Melinda May who were trapped with a prison staff infected by Bauer. Fitz provided the team with several syringes, explaining how it worked.
Quake, Davis and Prince found Coulson and May in the Penitentiary and injected the antidote to Warden Green and his officer. Meanwhile, Alphonso Mackenzie was infected by Hugo, but injected himself with the antidote before he could suffer from the disease.
When activated, the syringe displays four little stings which go through the patient's skin to deliver the Ghost Infection Antidote in the organism. The antidote directly counters the effects of the disease induced by the ghosts' touch and acts with immediate effects. However, the injection causes pain to the patient as the antidote must be injected directly in the brain stem, meaning that the needle must be put right above the neck at the base of the patient's skull.