The Johnson & Johnson COVID vaccine is a viral vector vaccine.
Viral Vector vaccines use another virus to generate antibodies to fight deadly pathogens i.e. it triggers an immune response by using a modified version of a different virus, known as a vector. For coronavirus, the J & J team took an adenovirus, a type of common cold virus, which when injected into someone’s arm, attaches itself to the cells that read the genetic instructions needed to make the SARs-COV-2 spike protein.
Following the production of spike protein, the immune system detects these invaders and creates antibodies.
Pfizer and Moderna on the other hand have been developed through Messenger RNA (mRNA) technology. The mRNA vaccines trigger an immune response by activating cells to fight the deadly pathogens. In terms of coronavirus, this type of vaccine instructs the cells to make a protein or a piece of coronavirus spike protein that produces an immune response in the body. This in turn creates antibodies needed to battle the deadly SARs-COV-2 virus.