Cochlear Implants are not for everybody and you have to be tested by a doctor to determine if you're a good fit to have a Cochlear Implant put in.
You can have a Cochlear Implant put in as long as you're eligible for the implant at any age at or above 12 months of age.
So a 12 month old can have a Cochlear Implant put in to correct hearing if needed and if they meet the requirements for the implant.