Calculation of pharmacokinetic parameters and the dose of factor VIII for prophylactic during phase 3 will be performed at the Department of Pharmaceutical Biosciences, Uppsala University, under the supervision of Professor Bjorkman using NonmemR software. The factor VIII levels, time and dose of factor VIII infusions and patients' weight will be sent to Uppsala. No other information will be sent. The dose recommendation will be sent to the treating centre by secure email within 7 days. The local centre will use the same information available to Uppsala and the TCIworksR software to calculate the patients' pharmacokinetics and dose recommendations. The dose recommendation of Uppsala will be used if the local recommendation is different.