A further possible outcome of inserting the DNA of a virus into genes within a human cell is that the cell may turn cancerous, or DNA antibodies could be produced which attack the cell itself, causing an auto-immune disease. If the DNA in a cell begins continually producing protein, this too can have negative consequences. In short, the safety of gene-based approaches to treatment has to be very carefully studied.
此外，病毒的 DNA 嵌入人體細胞本身的基因中，有可能產生癌化；也有可能產生抗 DNA 的抗體出來攻擊自己的細胞，造成自體免疫疾病；存在細胞內的 DNA 如果不停地表達、不斷產生蛋白，反而會造成不反應現象等等問題，基因製劑的安全性，仍需仔細研究克服。