Lack of volunteers for vaccine.
D016915:AIDS Vaccines / Q000008:administration & dosage*; D002986:Clinical Trials as Topic; D015658:HIV Infections / Q000517:prevention & control*; D006801:Humans; D007258:Informed Consent / Q000706:statistics & numerical data*; D008910:Minnesota; D018579:Patient Selection; D016312:Treatment Refusal; D014838:Volunteers / Q000706:statistics & numerical data
D016915:AIDS Vaccines