A number of leading SARS-CoV-2 vaccine candidates use other viruses, such as adenoviruses tagged with just one coronavirus protein, particularly the spike protein which is required for the virus to enter cells.
However, it is unlikely that these vaccines will induce strong and lasting protection against SARS-CoV-2. We believe that it is important to develop vaccines that cover as many SARS-CoV-2 proteins as possible but without any pathogenic potential.