Gene therapy and mRNA vaccines use similar delivery technologies which in general fall under the method of in vivo transfection. Transfection is a method of delivery. Not all transfections are gene therapies, they are not equivalent. Gene therapy involves delivering genetic material (DNA or RNA) that can a) code for and facilitate the expression an upstream regulator/transcription factor for modulation native DNA, b) contain targeted splicing factors for insertion or editing of native DNA; both of which necessitate additional delivery machinery (viral or non-viral vectors) to facilitate the entry of the genetic material into the nucleus. mRNA vaccines differ fundamentally in the fact that they do not enter the nucleus and lack the vectors to enter the nucleus and affect native DNA. Moreover, the genetic material introduced is often engineered to include sites for ubiquitin modification which makes sure there is controlled turnover of any protein translated and that it's expression is not sustained. But surely you should know that right?