Vaccine Adjuvants: The Current Necessity of Life

Context: Vaccination is considered as the most cost effective method for the prevention of human diseases. For this prevention method, we need certain substances to increase or boost the antibody as well as cell-mediated immune response against various bacterial as well as viral pathogens. Until now, alum was considered as the safest adjuvant for human use, licensed by the United States Food and Drug Administration. Due to the poor adjuvanticity of alum, conventional vaccines require multiple recall injections, at different time intervals, to attain or sustain the optimal immune response. The present review discusses about the necessity of adjuvants for vaccines. Evidence Acquisition: A number of factors such as slow release of antigen (depot effect), more efficient delivery of antigen to draining lymph nodes, non-specific activation of antigen-presenting cells or of B and/or T-lymphocytes, increased uptake of antigen by antigenpresenting cells or increased recruitment of immune cells to the site where the antigen is present, can contribute to increased immune responses to immunization. Many of these factors involve the interaction of various immune system components and specific anatomical features, making them difficult to replicate in model systems in vitro. Results: Despite the development of many potent adjuvant formulations with vaccine antigen during the last 80 90 years, aluminum compounds are still the only approved adjuvants used for routine human vaccines. Conclusions: Based on pre-clinical and preliminary clinical observations, it appears that the range of adjuvants accepted for human vaccines will expand in the coming years.