CMV disease can be prevented during this time in most people by using drugs that can kill the virus such as Ganciclovir, Foscarnet, or Cidofovir . However, these medications have many side effects and have to be given daily by vein for approximately 4-5 months after transplant. One of the side effects is that it takes the new immune system much longer to develop an effective defense against the virus. Therefore, once the medicines are stopped, the patients still have a chance to develop CMV disease.