Information has been received from a physician and an office receptionist concerning a 15 month old white male patient with no allergies or pre-existing medical history, who on 01/12/2005 was vaccinated in the left thigh with a first dose of varicella virus vaccine live.  Concomitant therapy administered on 01/12/2005 included a dose of diphtheria toxoid pertussis vaccine tetanus toxoid.  It was reported that the patient had an upper respiratory infection at the time of vaccination.  It was reported that 3 weeks after the vaccination on 02/02/2005, the patient developed cerebulitis, ataxia, and difficulty walking.  Follow up information from the physician indicated that the patient's ataxia started on 02/20/2005 and progressed by 02/25/2005 when he was seen.  The patient was admitted to the hospital for 2 days.  It was reported that the patient had a CT scan, his cerebrospinal fluid tested for HSV and varicella (wild and osaka) and no results were reported.  It was also noted that an MRI was pending a neurology consult.  The patient was not recovered.  Ataxia was ongoing.  A product quality complaint was not reported.  Additional information was received from the physician who confirmed that the patient did have an upper respiratory infection at the time of vaccination but otherwise had no medical history.  Approximately 3 weeks post-vaccination, the patient developed fussiness and irritability.  This progressed to shaking with balance problems, ataxia, and to his current status of not walking.  He was diagnosed with cerebellar ataxia and was initially hospitalization for 2 days.  A neurologist readmitted the patient to the hospital on approximately 03/04/2005 for IV methylprednisone and he was discharged on approximately 03/09/2005.  At the time of discharge, he was prescribed oral steroids.  The patient had a CT scan which was negative.  An MRI showed probable demyelination.  The patient had PCR analysis from cerobrospinal fluid which was negative for HSV, wild-type and osaka vaccine strain.  It was noted that his final cultures were fine.  The patient was to see the neurologist on 03/15/2005 and he was still not walking.  The physician reported that since the patient had no known health history they were not sure what could be causing the patient's experiences.  The physician explained to the parents that he had seen cases of ataxia with active chickenpox. so it was possible that it could be related to the vaccine, however, through his research there was no data to support this.  Additional information has been requested. This is in follow-up to report(s) previously submitted on 5/16/2005. Information has been received from a physician and an office receptionist concerning a 15-month-old male patient with no allergies or pre-existing medical history, who on 12-JAN-2005 was vaccinated in the left thigh with a first dose of VARIVAX (Merck) (lot # 646819/1065N). Concomitant therapy administered on 12-JAN-2005 included a dose of DTP (unspecified). It was reported that the patient had an upper respiratory infection at the time of vaccination. It was reported that three weeks after the vaccination on 02-FEB-2005, the patient developed "cerebulitis," ataxia, and difficulty walking. Follow-up information from the physician indicated that the patient's ataxia started on 25-FEB-2005 and progressed by 25-FEB-2005 when he was seen. The patient was admitted to the hospital for two days. It was reported that the patient had a CT scan, his cerebrospinal fluid was treated for HPV and Varicella (wild and Osaka") and no results were reported. It was also noted that an MRI was pending a neurology consult. The patient was not recovered. Ataxia was ongoing. A product quality complaint was not reported. Additional information was received from the physician who confirmed that the patient did have an upper respiratory infection at the time of vaccination but otherwise had no medical history. Approximately three weeks post vaccination, the patient developed fussiness and irritability. This prgressed to shaking with balance problems, ataxia, and to his current status of not walking. He was diagnosed with cerebellar ataxia and was initially hospitalized for two days. A neurologist readmitted the patient to the hospital on approximately 04-MAR-2005 for IV methylprednisone and he was discharged on approximately 09-MAR-2005. At the time of discharge he was prescribed oral steroids. The patient had a CT scan which was negative. An MRI showed probable demyelination. The patient had PCR analysis from cerebrospinal fluid which was negative for HSV, wild-type and "Osaka" vaccine strain. It was noted that his final cultures were fine. The patient was to see the neurologist on 15-MAR-2005 and he was still not walking. The physician reported that since the patient had no known health history they were not sure what could be causing the patient's experiences. The physician explained to the parents that he had seen cases of ataxia with active chickenpx, so it was possible that it could be related to the vaccine, however, through his research there was no date to support this. Additional information has been requested.