Both components of the proposed vaccine have been tested individually. Non-replicating adenoviruses have been through clinical safety-testing and adenoviral vectors in general have been used safely in thousands of people across a wide range of ages. It is much faster to manufacture the clinical grade peptides necessary for coating the adenovirus, than re-engineering and manufacturing a new virus, making this approach more flexible and enabling clinical testing to progress quickly in the event that a new coronavirus strain emerges.
Most vaccines focus on boosting the antibody B cells response, but a T-cell immune response is important given that the infection targets the respiratory tract. COVID-19 replicates particularly fast and it appears that, by the time neutralizing antibodies are produced, many cells in the lungs have already become infected and require cell-mediated clearance. Adenoviral vectors are particularly strong at inducing T-cell mediated immune responses, and it is hoped that the SARS-COV-2 spike proteins will be processed to induce both T-cell and antibody mediated immunity to COVID-19. Additionally coating the adenovirus with peptides specifically selected for driving CD-8+ T-cells is expected to further enhance the cell mediated immune response; with the added capacity to broaden the immune targets.