Patient Interview Study to Explore the Impact of Gene Therapy in Hemophilia A & B

The purpose of this study is to learn about experiences of patients with hemophilia A and B after taking gene therapy. The experiences of patients will be studied through online interviews. This study is seeking participants who are: * part of the Pfizer's gene therapy clinical studies or * in the long-term follow up for these clinical programs. Participants will have one study visit at the clinic and one online interview. The planned duration for each participant will be 1 to 2 months. This covers the time from entering the study to end of the online interview.