Shortly after the discovery of the different so-called monogenic genes (one gene = one disease), the medical and scientific community became excited by the prospects of development and implementation of clinical trials in gene therapy aimed at correcting failing genetic activity. Following the death of a patient with severe combined X-linked immunodeficiency, widely reported in the scientific community, it was obvious that there was still much progress to be made in the 2000s for recognized gene therapies to be implemented. However, new vectors derived from lentiviruses and adenoviral vectors are currently in development, which promise to be more efficient and safer, with positive outcomes in several clinical trials on hemophilia, adrenoleukodystrophy, Leber's amaurosis, or cancer.