Viral Vector Vaccines

Viral vector vaccines use harmless, non-replicating or replicating viruses to deliver genetic material for production of vaccine antigens into host cell cytoplasm. While viral vector vaccines may theoretically induce life-long immunity with low antigen concentrations, their attenuation, safety and spread to the community are of concern. Vaccines based on recombinant viral vectors can induce both humoral and cellular immune responses. Adenovirus vectors are versatile gene transfer vectors that can be easily manufactured, and which may allow simultaneous expression of multiple antigens by a single vector construct. Adenovirus vector vaccines based on the adenovirus Ad26 vector have been widely used as vaccines against Ebola and COVID19 (see Chapters 44 and 56). A common concern of using viral vector vaccines is pre-existing immunity or induction of immunity against the vector itself, but in some circumstances it has no meaningful impact and it can be resolved in several ways. Several harmless viruses are already used as vectors for innovative vaccines and many more are in research.