Viral vectors as vaccine platforms: from immunogenicity to impact

•Safety and potency of simian adenovirus vectors is now well established, most recently in infants.•Viral vectored vaccines are effective against malaria and Ebola in field trials.•Protective mechanisms involve both CD8+ T cells and neutralising antibodies.•Vaccine manufacture is sufficiently scalable to enable a rapid response to outbreaks.

Viral vectors are the vaccine platform of choice for many pathogens that have thwarted efforts towards control using conventional vaccine approaches. Although the STEP trial encumbered development of recombinant human adenovirus vectors only a few years ago, replication-deficient simian adenoviruses have since emerged as a crucial component of clinically effective prime-boost regimens. The vectors discussed here elicit functionally relevant cellular and humoral immune responses, at extremes of age and in diverse populations. The recent Ebola virus outbreak highlighted the utility of viral vectored vaccines in facilitating a rapid response to public health emergencies. Meanwhile, technological advances in manufacturing to support scale-up of viral vectored vaccines have helped to consolidate their position as a leading approach to tackling 'old' and emerging infections.