sorry how is the vaccine gene therapy but the corona virus or any other virus not gene therapy?
viruses also inject their own DNA or RNA in your cells to produce more of its kind. the only difference now is that mRNA and DNA vaccines only inject a fragment of the RNA the virus would have injected. Also since the information to replicate its self is not added to the vaccine, fewer cells are affected by the vaccine, than if you were infected by the virus.
viruses have already become part of our DNA. viruses have infected us for millions of years, to a point that 8% of your DNA is virus.