The thing that always bothered me about the two original covid-19 vaccines were that they they were using mRNA to program codes into your cells. The new Johnson & Johnson vaccine however uses a dead virus like all other original vaccines used to use. I'm not going to get any of those vaccines but it seems that if someone wants to then the Johnson and Johnson would be the safest way to go.
What is the difference between how the Johnson & Johnson vaccine works and how the Pfizer and Moderna vaccines work?
The ultimate difference is the way the instructions are delivered. The Moderna and Pfizer vaccines use mRNA technology, and the Johnson & Johnson vaccine uses the more traditional virus-based technology.
mRNA is essentially a little piece of code that the vaccine delivers to your cells. The code serves as an instruction manual for your immune system, teaching it to recognize the virus that causes COVID-19 and attack it, should it encounter the real thing.
Instead of using mRNA, the Johnson & Johnson vaccine uses a disabled adenovirus to deliver the instructions. This adenovirus is in no way related to the coronavirus. It is a completely different virus. Although it can deliver the instructions on how to defeat the coronavirus, it can't replicate in your body and will not give you a viral infection...
Johnson and Johnson vaccine How is it different | VCU Health.