Immunocompromised patients have increased susceptibility to vaccine-preventable infections. Thus, vaccination is a critical issue in this population. Vaccines are usually classified as live versus inactivated or subunit (nonviable) vaccines. In general, inactivated vaccines are safe in immunocompromised patients and should be given per the routine schedule except when they are unlikely to have any benefit as in severe antibody deficiency or combined immunodeficient patients and patients receiving immunosuppressive therapy or immunoglobulin replacement. However, viable vaccines usually carry the risk of causing disease, especially in severely immunocompromised patients. Therefore, much greater caution must be exercised with the use of viable vaccines and administration is individualized on the basis of the estimated risk of infections if not vaccinated versus the potential adverse effects of the vaccine itself. In this review, we make clear recommendations on the basis of available evidence regarding both routine and specialized vaccines, viable and nonviable, and the degree of immune compromise in all the categories of immunodeficiency disorders. (C) 2016 American Academy of Allergy, Asthma & Immunology.