Experimental: 1-<2 years post stem cell transplant

At Visit 1 participants will be given information about the nature of HZ and its recognition and given a questionnaire for completion should they develop HZ during the study. They will also be asked to contact the study team if they develop HZ so that further evaluation of potential HZ is completed and the details of the event recorded. A swab of an active lesion or crust from a dried lesion will be obtained for VZV PCR. A participant who develops HZ will be asked to complete the questionnaire weekly for 4 weeks and then at 8 and 12 weeks. In addition, the subject will be asked about pain medications taken during the episode. Information on HZ incidence will be supplemented from the clinic medical records and the electronic medical records. Subjects will be followed for 1 year after enrollment for the occurrence of HZ and of post-herpetic neuralgia (PHN).

Experimental: 2-<3 years post stem cell transplant

At Visit 1 participants will be given information about the nature of HZ and its recognition and given a questionnaire for completion should they develop HZ during the study. They will also be asked to contact the study team if they develop HZ so that further evaluation of potential HZ is completed and the details of the event recorded. A swab of an active lesion or crust from a dried lesion will be obtained for VZV PCR. A participant who develops HZ will be asked to complete the questionnaire weekly for 4 weeks and then at 8 and 12 weeks. In addition, the subject will be asked about pain medications taken during the episode. Information on HZ incidence will be supplemented from the clinic medical records and the electronic medical records. Subjects will be followed for 1 year after enrollment for the occurrence of HZ and of post-herpetic neuralgia (PHN).

Experimental: ≥ 3 years post stem cell transplant

At Visit 1 participants will be given information about the nature of HZ and its recognition and given a questionnaire for completion should they develop HZ during the study. They will also be asked to contact the study team if they develop HZ so that further evaluation of potential HZ is completed and the details of the event recorded. A swab of an active lesion or crust from a dried lesion will be obtained for VZV PCR. A participant who develops HZ will be asked to complete the questionnaire weekly for 4 weeks and then at 8 and 12 weeks. In addition, the subject will be asked about pain medications taken during the episode. Information on HZ incidence will be supplemented from the clinic medical records and the electronic medical records. Subjects will be followed for 1 year after enrollment for the occurrence of HZ and of post-herpetic neuralgia (PHN).