The JNJ COVID-19 vaccine, known as the JNJ-78436735, utilizes a recombined adenovirus vector, human Ad26.COV2.S., which expresses the S-subunit of the SARS-CoV-2 virus to induce an immune response. Basically, the adenovirus vector “carries” the genes for the S-subunit to the cell which will reproduce the protein, then inducing the immune response.

AKA, NOT mRNA.