Vectorvaccins

Vectorvaccins (vector vaccines) are a class of vaccines that use a harmless delivery system, or vector, to introduce genetic material encoding an antigen from a pathogen into a recipient's cells. The vector is engineered to be non-pathogenic and to deliver one or more genes that instruct host cells to produce the target antigen. The immune system responds to the expressed antigen with antibody and T-cell responses, aiming to provide protection against the pathogen.

Viral vectors are the most common platform and include non-replicating vectors, such as certain adenoviruses and chimpanzee adenoviruses, and replicating vectors that can persist longer. Other viral vectors include vesicular stomatitis virus. Bacterial vectors, such as Listeria monocytogenes or Salmonella-based systems, are studied but less widely used. Notable examples of viral-vector vaccines include Ebola vaccine rVSV-ZEBOV and COVID-19 vaccines that use Ad26.COV2.S or ChAdOx1-S, illustrating the range of vector choices and delivery strategies.

Advantages of vector vaccines include the potential to elicit strong humoral and cellular immunity, the possibility of single-dose regimens, and the ability to present antigens in their native cellular context. Limitations include pre-existing immunity to common vector serotypes, safety concerns for certain replicating vectors, manufacturing complexity, and potential anti-vector immune responses that can reduce efficacy on repeated doses. Storage and distribution requirements vary by platform.

Vector vaccines are approved for several infectious diseases and are actively developed for cancer and other conditions. Many candidates are in clinical trials, and research continues to improve safety, stability, and the ability to bypass vector immunity, as well as to expand the range of vectors and delivery routes.