- Known or suspected immunodeficiency (e.g. HIV infection, primary immunodeficiency disorder, leukemia, lymphoma), use of immunosuppressive or antineoplastic drugs (corticosteroids> 10 mg prednisolone/prednisone, or equivalent, for mare than 14 days in the last three months). Persons with previous skin cancer or cured non-lymphatic tumors are not excluded from the study.