Methods of eliciting an immune response to a JC polyomavirus (JCV) by administering an effective amount of an immunogenic composition including an isolated JCV VP1 polypeptide or a nucleic acid encoding the VP1 polypeptide to a subject are provided. VP1 polypeptides and immunogenic compositions suitable for use in the methods are provided, including JCV genotype 2 VP1 polypeptides and/or JCV genotype 3 polypeptides. Methods of identifying a subject at risk of developing progressive multifocal leukoencephalopathy (PML) are also provided. In some embodiments, the methods include obtaining a biological sample from a subject, detecting presence or absence of JCV neutralizing antibodies in the sample from the subject, and identifying that the subject is at risk of developing PML if there is an absence of detectable JCV neutralizing antibodies in the sample from the subject.