When you look into the J&J it is just a different delivery system. https://www.stamfordhealth.org/healthflash-blog/infectious-disease/johnson--johnson-covid-19-vaccine/

" The Johnson & Johnson vaccine is an adenovirus (or viral) vector vaccine while both the Pfizer and Moderna vaccines use mRNA technology. "Adenovirus" is the term for common viruses that cause a range of illnesses.

Having an adenovirus vector vaccine means you are injecting a modified version of the adenovirus into your cells which delivers important information in the form of a gene. This results in our cells making a small fragment of the SARS-CoV-2 virus called the spike protein, which triggers an immune response.  Viral vector vaccines do not alter your DNA in any way.  The mRNA vaccines made by Moderna and Pfizer deliver mRNA in a lipid envelope which stimulates cells to make spike protein resulting in the same immune response. " 

When you look into the J&J it is just a different delivery system of the Mrna.