ABSTRACT
The goal of vaccination is to provide protection against a particular infection. Vaccines induce protection through a variety of immune mechanisms. Understanding the immune mechanisms, often referred to as “immune correlates of protection,” can facilitate the rational design of vaccines. The humoral immune response through the production of antibodies appears to be the immune correlate by which a majority of current vaccines induce protection, most notably against viral or bacterial infections. For many other infectious diseases, however, the cellular immune response through CD4+ and CD8+ T cells is also important for immune protection. Indeed, a major impediment to the development of successful vaccines against HIV, malaria, and Mycobacterium tuberculosis infection has been the failure to induce and sustain long-term cellular immune responses sufficient to mediate protection. Thus, in considering vaccine design, especially for the aforementioned infections in which cellular immune responses might be critical in mediating protection, attention should be given not only to maximizing the magnitude of the immune response but also to the qualitative aspects of the immune response.
