Patients will first get Td preconditioning and a medicine called temozolomide for 5 days. On day 21, they will get the study vaccine, PEP-CMV. The first 3 vaccines will be given every 2 weeks. After that, the vaccines will be given once a month. The first treatment cycle lasts 77 days, and all cycles after that last 28 days. To join the study, patients must have lab and clinical tests done within 7 days before starting. Lab results must be no more than 7 days old when therapy begins. If therapy starts within 7 days of the lab tests, the tests do not need to be repeated.

Patients can join this study if they have a brain tumor called medulloblastoma that has come back, is getting worse, or did not improve with treatment. Doctors must confirm the tumor by looking at it under a microscope, either when it was first found or when it returned.

Patients need to have a type of brain tumor called medulloblastoma that has come back, is getting worse, or did not respond to treatment. Doctors must confirm the tumor by looking at tissue samples either when the patient was first diagnosed or when the tumor returned.

The study wants to learn three things:
1. How many patients with medulloblastoma can live at least 4 months without their tumor getting worse.
2. How many patients with DIPG live for 1 year after getting radiation and the PEP-CMV vaccine.
3. How many patients with HGG live for 1 year without their tumor getting worse after radiation and the PEP-CMV vaccine.