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No doubt vectors are contributing to difficulties with gene therapies, but without having read the previous articles, the severe life-threatening side effects seen in these cases are caused by immune system recognition of the transgene as non-self, rather than the vector. They're getting given the genes they never had at birth and the immune system isn't liking it. If it were the vector the reaction would occur quickly - like when you get given a vaccination - these boys are getting severe auto-immune complications 3-6 weeks post dosing.