COVID-19 viral vector vaccine webpageMany vaccines use a weakened or inactivated form of the target pathogen to trigger an immune response.
Viral vector vaccines use a different virus as a vector instead, which delivers important instructions (in the form of a gene) to our cells.
For COVID-19 vaccines, a modified virus delivers a gene that instructs our cells to make a SARS-CoV-2 antigen called the spike protein.