The failures of gene therapy illustrate that the technology is not 100% effective. Scientists are working on solutions to the problems and it is only a matter of time before gene therapy will be available with new and safer vectors. In each case it will be necessary to make a risk/benefit appraisal, where alternative treatments can be balanced against the pros and cons of gene therapy. Of course with better genetic testing it is increasingly a question of parental choice whether foetuses carrying these mutations are allowed to develop to full tern. This question will be even more poignant when individuals who have undergone gene therapy, but who still carry the mutation in their germs cells, want to have children.