re: Info on Johnson & Johnson’s Covid vaccine

It is more traditional in the sense that a non-replicating, non-viable virus with a gene for the Covid spike protein enters the immune cells and stimulates the immune response based on the production of this spike glycoprotein . Even though Rubella and Measles are not vector viruses (since they don't have added genes from another bacteria or virus), the immune response is generated in the same way, i.e. against a glycoprotein on the attenuated virus.

mRNA vaccines are non-conventional in that no attenuated viral cells enter the immune cells to stimulate an immune response. The mRNA that enters the cells and is solely responsible for production of the protein that stimulates the immune response. This is the first ever mRNA vaccine released for wide spread use. One of the concerns in previous studies on this type of vaccine was the effect it may have on causing an autoimmune response.