Coma, From the Greek koma, meaning deep sleep, is a profound state of unconsciousness where the patient cannot be awakened, fails to respond normally to pain or light, does not have sleep-wake cycles, and does not take voluntary actions. Coma may result from a variety of conditions, including intoxication, metabolic abnormalities, central nervous system diseases, acute neurologic injuries – including vaccination.

Comas generally last a few days to a few weeks, and rarely last more than 2 to 4 weeks. After this time, some patients gradually come out of the coma, some progress to a vegetative state, and others die.