Abstract
Vaccine development is one of the most significant achievements of humans in Biomedicine. These vaccines are usually supplemented with adjuvants to enhance immunity. Apart from alum which is recognized as the gold standard, one may increase the quality of the vaccine by adding other adjuvants or agents that boost the immune response with improved delivery vehicles such as liposomes, immune-stimulating complexes (ISCOMs), and micro/nanospheres. Adjuvants stimulate the effectiveness of a vaccine by activating the immune system to respond more strongly to the vaccine, resulting in enhanced immunity to a particular disease/antigen. Adjuvants do this by imitating specific sets of identical molecular sequences like lipopolysaccharides (LPS), bacterial cell wall basic constituents, and endocytosed nucleic acids such as double-stranded deoxyribonucleic acid (dsDNA), single-stranded ribonucleic acid (ssRNA), and unmethylated CpG-dinucleotide containing deoxyribonucleic acid (DNA). Apart from incorporating adjuvants to improve vaccine quality, the delivery system also is an important aspect of vaccine development. The development of next-generation technology has been explored to generate a vaccine with the same efficacy as the original live-attenuated and inactivated vaccines, but without the hazards and limitations that come with them, including their delivery methods. These novel vaccines have explored methods for targeted delivery of antigenic material, as well as for the control of release profiles so that dosing regimens can be matched to the timelines of immune system stimulation and the realities of healthcare delivery in dispersed populations. This review covers vaccination adjuvants and delivery vehicles that are currently in use/still developing.

Key words: Adjuvant, immunity, antigen, delivery systems, vaccines