Host Background Immunity and Human Immunodeficiency Virus Protective Vaccines, a Major Consideration for Vaccine Efficacy in Africa and in Developing Countries

The AIDS epidemic is clearly the worst epidemic of the last century. Over 23 million individuals have already died from AIDS, and more than 36 million people are infected by human immunodeficiency virus type 1 (HIV-1), especially in Africa and Southeast Asia (36). It is estimated that more than 100 million people will be carrying the virus in less than 10 years (36). The only plausible way for diminishing this epidemic, aside from social and educational measures, is by mass vaccination. Regrettably, despite two decades of intensive efforts, no anti-HIV vaccine is yet available. Two critical issues have to be considered as prerequisites for developing an effective HIV vaccine: first, what type of immune response is needed to confer optimal protection against HIV-1, and second, what is the role of the preexisting immune profile of the host in its capacity to mount a potent protective immune response following vaccination.