From the paper:
The COVID vaccines (from Oxford/AstraZeneca, Pfizer/BioNTech, and Moderna) ALL work by getting our cells to make copies of the virus spike protein. The Oxford vaccine achieves this by introducing the spike protein gene via an adenovirus vector. The other two vaccines deliver the spike protein gene directly as mRNA wrapped in a nanoparticle.
But not the JNJ? It’s a little over my head. I understand the mRNA (and I guess the AZ as well) trigger the immune system to make its own covid-looking spike protein which the immune system then attacks, training the memory t-cells to kill covid. Not quite sure I understand how the JNJ vaccine works.