Immunological effects of adjuvants, their mechanisms, and relevance to vaccine safety

Abstract

The purpose of this review is to provide a general overview of adjuvants as immune potentiators, and to offer new insights into the immunological basis and molecular mechanisms of their action. Adjuvants are a key component of many vaccines and their use and development enables many avenues of vaccine design that would otherwise be impossible. Nevertheless, adjuvants are often associated with many safety concerns. Search of available medical literature on adjuvants, vaccines, and their mechanisms of action was performed. Additional articles were identified based on citations in retrieved articles. The main role of adjuvants is to trick the immune system in perceiving vaccine antigen as a serious threat, and thus initiate innate and consecutively adaptive response mechanisms, including long-term immune memory to that antigen. Adjuvants do that by triggering the same evolutionary conserved mechanisms that innate immunity utilizes to detect danger. By inducing innate immune reaction, adjuvants can concurrently provoke some undesirable immune response. However, serious adverse reactions to adjuvanted (as well as nonadjuvanted) vaccines are extremely rare, and there are carefully elaborated regulatory mechanisms to ensure that risks of such adverse reactions are kept at minimum.

Conclusion - The use of adjuvants allows a great variety of vaccine designs, enabling the development of safer, more effective, more optimized, and more accessible vaccines than it would be possible without adjuvants. Despite frequent calls to debate, all currently used adjuvanted vaccines have repeatedly demonstrated an excellent safety profile and remain one of the principal tools of science-based medicine in preventing infectious diseases.