Persons exposed to smallpox should be vaccinated with a replication-competent vaccine, unless they are severely immunodeficient, according to a guideline from the Centers for Disease Control and Prevention.
Severely immunodeficient persons won’t benefit from a smallpox vaccination because there will likely be a poor immune response and heightened risk of negative events. These include bone marrow transplant recipients within 4 months of transplantation, people infected with HIV with CD4 cell counts <50 cells/mm3, persons with severe combined immunodeficiency, complete DiGeorge syndrome patients, and people with other severely immunocompromised states requiring isolation.
“If antivirals are not immediately available, it is reasonable to consider the use of Imvamune in the setting of a smallpox virus exposure in persons with severe immunodeficiency,” the CDC added.
Find the full guideline in the MMWR (February 20, 2015 / 64(RR02);1-26).