AbstractVaccination has indubitably made noteworthy contribution to global health. Recent years have witnessed the employment of subunit antigens rather than inactivated or live attenuated vaccines, owing to the superior safety of the former. The intrinsic weak immunogenicity of subunit antigens makes it imperative to formulate them with an adjuvant. Presently, the armamentarium of approved vaccine adjuvants is very poor. Nanocarriers hold great promise for successful vaccine delivery owing to their versatility, excellent cellular uptake properties, capacity to protect antigen, amenability to targeting, and ability to offer prolonged antigen presentation. All these attributes ultimately endow nanocarriers with immense potential to achieve needle-free vaccine delivery, reduce the number of vaccinations, attain dose sparing of antigen, and lead to stronger immune response generation. Nanocarriers can be explored in manifold ways to accomplish targeted antigen delivery to antigen presenting cells. They can be formulated to contain both antigen and immunostimulant molecules, and they can be engineered from specific materials to achieve antigen presentation through the desired pathway to stimulate a particular arm of the immune response. This review discusses the basics of immune response generation, mechanisms of adjuvanticity by nanocarriers, parameters influencing their adjuvanticity, and finally describes the incredible opportunities offered by a gamut of nanocarriers for vaccine delivery
