Scientific background on the risk engendered by reducing the lifetime blood donation deferral period for men who have sex with men.

The lifetime deferral for men who have sex with men (MSM) has not been harmonized with the 12-month deferral for similar-risk activities through heterosexual contacts. This occurs primarily because of fears of increased transfusion transmission of known sexually and transfusion-transmitted viruses for which donor blood is (eg, HIV) or is not (eg, human herpesvirus 8 [HHV-8]) tested and also of fears of novel agents that may share the epidemiology and long asymptomatic phase of HIV. A 12-month MSM deferral could result in release of 1 HIV-infectious donation every 11 years in the United States. This risk is smaller than the risk from allowing the continued use of pooled whole blood-derived platelets (release of 1 infectious platelet dose every 1.67 years), a risk that is considered "tolerable." Provided that measures to reduce the number of allogeneic-donor exposures to novel pathogens (which may be vector- or food-borne rather than sexually transmitted) are implemented, and the deferral for similar-risk activities through heterosexual contacts is extended to 5 years, a 5-year MSM deferral could be justified because of the interval between emergence of a novel pathogen and introduction of measures to protect the blood supply. Also, provided that measures to protect the blood supply from HHV-8 are implemented, a lifetime MSM deferral could be justified because of the uncertainty about the clinical consequences of transfusion transmission of HHV-8. Because such alternate measures, which would have had a greater impact on safety than the MSM deferral, have not been implemented to demonstrate a consistent approach to safety, maintenance of the current MSM deferral appears to be selectively precautionary and cannot be justified.