evidence: The data relating death and measles or mumps vaccine are from case reports and case series. The largest series comes from India, but TSS caused by the unhygienic conditions involved in the immunization program was the apparent cause of death reported for eight of nine patients. Evidence based on RNA sequencing techniques has linked measles vaccine and measles infection to subsequent death in some severely immunocompromised children. In contrast, studies of the immunogenic response to measles vaccine in children infected with human immunodeficiency virus (HIV), which causes acquired immune deficiency syndrome (AIDS), have not recorded any deaths from measles vaccine-strain viral infection.