Well, you don't know how biology works. Inactive viruse is not very efficient to call an immune reponse. Even myself, i have a hard time understanding it because it is technical and i have to slowly reread study.

It is very technical and the result of decade of research by scientifics, they started the first mRNA vaccine in 1990. It is also a very promising solution against cancer.

• https://www.vumc.org/viiii/infographics/how-does-mrna-vaccine-compare-traditional-vaccine
• https://pmc.ncbi.nlm.nih.gov/articles/PMC5906799/