The serum levels of anti-tat antibodies, tat protein, and p24 protein are predictive of disease progression in HIV infected individuals and serve as prognostic markers. The present invention relates to a method for determining the prognosis of an HIV infected individual by measuring serum levels of one or more of these prognostic markers. In addition, a method for monitoring whether an HIV infected individual is in need of immunization with a tat vaccine and a method for monitoring the efficacy of immunization with a tat vaccine are also disclosed.