This study will test how well a new medicine called concizumab works for participants who have haemophilia A or B with or without inhibitors. The purpose is to show that concizumab can prevent bleeds and is safe to use. Participants will have to inject the study medicine every day under the skin with a pen-injector. The study will last for at least 2 years and up to about 4 years. The length of time the participant will be in the study depends on if the study medicine will be available for purchase in their country.