Can you explain the difference between what you just said and the Johnson adenovirus thing?
The objective of both vaccines (Pfizer/ J&J) is to create spike proteins inside the recipient. It's how they do it that's different.
Pfizer uses mRNA which is like a recipe book containing the recipe for the spike protein. This is injected directly into the recipient. As I said earlier it's a short lived recipe book. It enters the cells, delivers the recipe and disintegrates within 72 hours. It does not "interfere" with the cell's DNA as the scaremongers have been saying.
J&J uses a more traditional method. Here the 'recipe' is loaded into the DNA of an unrelated virus (called adenovirus 26). This virus has been 'neutered' so it doesn't replicate or cause any harm. It simply acts as a carrier. The carrier virus carrying the recipe enters a cell and heads straight for the nucleus where the genetic machinery is. The host cell starts making spike proteins some of which sprout on its surface. The immune system which is constantly surveying the body for suspicious or unknown proteins see these and gets into action. The rest is the same.
The key difference is, with pfizer you are injecting the recipe directly into the cells. With J&J you are letting an unrelated virus act as the delivery man to carry the recipe inside the cells. The pfizer/mRNA for obvious reasons is more efficient -- and also more effective at protecting against covid (93% vs ~70% )