Bleeding episodes were classified as spontaneous if participant records a bleeding event when there is no known contributing factor such as definite trauma/antecedent strenuous activity. In addition, location of bleed (joint, internal, skin/mucosa or muscle) were also collected. Annualized spontaneous joint bleeding episodes=(Number of spontaneous joint bleeding episodes during efficacy period/number of days during efficacy period)*365.25. Efficacy period reflects sum of all intervals of time during which participants were treated with rFIXFc per treatment regimen excluding major and minor surgical/rehabilitation periods and large injection intervals. Bleeding episodes were summarized by treatment regimen for participants from study 998HB102 and by age cohort (<6 years and 6 to <12 years old) and treatment regimen for participants from study 9HB02PED as per planned analysis. Participants were included in summary of more than 1 treatment regimen if their regimen changed during study.

An exposure day is a 24-hour period in which one or more rFIXFc injections are given. The total number of days of exposure to rFIXFc were summarized by treatment regimen for participants from study 998HB102 and by age cohort (<6 years and 6 to <12 years old) and treatment regimen for participants from study 9HB02PED as per planned analysis. Participants were included in summary of more than 1 treatment regimen if their regimen changed during study.

Annualized consumption = (total international unit per kilogram [IU/kg] of study treatment received during the efficacy period / total number of days during the efficacy period) multiplied by 365.25. Efficacy period reflects sum of all intervals of time during which participants were treated with rFIXFc per treatment regimen excluding major and minor surgical/rehabilitation periods and large injection intervals. Annualized consumption was summarized by treatment regimen for participants from study 998HB102 and by age cohort (<6 years and 6 to <12 years old) and treatment regimen for participants from study 9HB02PED as per planned analysis. Participants were included in summary of more than 1 treatment regimen if their regimen changed during study.

Participants were assessed for response to their rFIXFc regimen using following 4-point scale: 1=Excellent: bleeding episodes responded to less than or equal to (<=)usual number of injections or dose of rFIXFc or rate of breakthrough bleeding during prophylaxis was <= that usually observed; 2=Effective: most bleeding episodes responded to same number of injections and dose, but some required more injections or higher doses, or there was minor increase in rate of breakthrough; 3=Partially Effective: bleeding episodes most often required more injections and/or higher doses than expected or adequate breakthrough bleeding prevention during prophylaxis required more frequent injections and/or higher doses and 4=Ineffective: routine failure to control hemostasis/hemostatic control require additional agents. Total number of scale responses =total count of scale responses for all participants; multiple responses per participant including those at scheduled and unscheduled visits are counted.

Using eDiary, participant received rating for treatment response to any bleeding episode (BE) using 4-point scale- 1=Excellent: Abrupt pain relief and/or improvement in signs of bleeding within approximately (approx.) 8 hours (h) after initial injection (inj.); 2=Good: Definite pain relief and/or improvement in signs of bleeding within approx. 8h after an injection, but possibly requiring more than 1 injection after 24-48h for complete resolution; 3=Moderate: Probable/slight beneficial effect within 8h after initial injection and requires more than 1 injection and 4=None: No improvement, or condition worsens within approx. 8h after initial injection. This assessment was to be made approx. 8 to 12h from time the injection was given to treat BE and prior to any additional doses of rFIXFc given for same bleeding episode. Percentages are based on the number of bleeding episodes for which a response (excellent or good) was provided for the first injection during the efficacy period.

Participants received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis: Participants received 20 international units per kilogram (IU/kg) to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile observed in parent study and individual pharmacokinetic profile, trough, and/or peak (recovery) values. Individualized prophylaxis: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized Prophylaxis: included addition of prevention doses prior to strenuous activity; targeting a FIX trough level of > 5 percent (%), if warranted by the bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such a regimen. Episodic (On Demand): The individual dose of rFIXFc to treat bleeding episodes was based on participants clinical condition, type and severity of the bleeding event.

Participants who have undergone major surgery or have major surgical/rehabilitation period in study.

Participants with 6 to <12 years old age received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis (P): 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile in parent study and individual pharmacokinetic profile, trough and/or peak (recovery) values; Individualized P: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized P: included addition of prevention doses prior to strenuous activity; targeting FIX trough level of > 5%, if warranted by bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such regimen. Participants who reached age of 12 during study could also choose to switch to episodic treatment group, with dosing based on participants clinical condition and type and severity of bleeding event.

Participants received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis: Participants received 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile observed in parent study and individual pharmacokinetic profile, trough, and/or peak (recovery) values. Individualized prophylaxis: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized Prophylaxis: included addition of prevention doses prior to strenuous activity; targeting a FIX trough level of > 5%, if warranted by the bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such a regimen. Episodic (On Demand): The individual dose of rFIXFc to treat bleeding episodes was based on participants clinical condition, type and severity of the bleeding event.

Participants with 6 to <12 years old age received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis (P): 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile in parent study and individual pharmacokinetic profile, trough and/or peak (recovery) values; Individualized P: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized P: included addition of prevention doses prior to strenuous activity; targeting FIX trough level of > 5%, if warranted by bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such regimen. Participants who reached age of 12 during study could also choose to switch to episodic treatment group, with dosing based on participants clinical condition and type and severity of bleeding event.

Participants received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis: Participants received 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile observed in parent study and individual pharmacokinetic profile, trough, and/or peak (recovery) values. Individualized prophylaxis: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized Prophylaxis: included addition of prevention doses prior to strenuous activity; targeting a FIX trough level of > 5%, if warranted by the bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such a regimen. Episodic (On Demand): The individual dose of rFIXFc to treat bleeding episodes was based on participants clinical condition, type and severity of the bleeding event.

Participants with 6 to <12 years old age received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis (P): 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile in parent study and individual pharmacokinetic profile, trough and/or peak (recovery) values; Individualized P: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized P: included addition of prevention doses prior to strenuous activity; targeting FIX trough level of > 5%, if warranted by bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such regimen. Participants who reached age of 12 during study could also choose to switch to episodic treatment group, with dosing based on participants clinical condition and type and severity of bleeding event.

Participants received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis: Participants received 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile observed in parent study and individual pharmacokinetic profile, trough, and/or peak (recovery) values. Individualized prophylaxis: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized Prophylaxis: included addition of prevention doses prior to strenuous activity; targeting a FIX trough level of > 5%, if warranted by the bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such a regimen. Episodic (On Demand): The individual dose of rFIXFc to treat bleeding episodes was based on participants clinical condition, type and severity of the bleeding event.

Participants with 6 to <12 years old age received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis (P): 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile in parent study and individual pharmacokinetic profile, trough and/or peak (recovery) values; Individualized P: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized P: included addition of prevention doses prior to strenuous activity; targeting FIX trough level of > 5%, if warranted by bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such regimen. Participants who reached age of 12 during study could also choose to switch to episodic treatment group, with dosing based on participants clinical condition and type and severity of bleeding event.

Participants received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis: Participants received 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile observed in parent study and individual pharmacokinetic profile, trough, and/or peak (recovery) values. Individualized prophylaxis: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized Prophylaxis: included addition of prevention doses prior to strenuous activity; targeting a FIX trough level of > 5%, if warranted by the bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such a regimen. Episodic (On Demand): The individual dose of rFIXFc to treat bleeding episodes was based on participants clinical condition, type and severity of the bleeding event.

Participants received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis: Participants received 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile observed in parent study and individual pharmacokinetic profile, trough, and/or peak (recovery) values. Individualized prophylaxis: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized Prophylaxis: included addition of prevention doses prior to strenuous activity; targeting a FIX trough level of > 5%, if warranted by the bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such a regimen. Episodic (On Demand): The individual dose of rFIXFc to treat bleeding episodes was based on participants clinical condition, type and severity of the bleeding event.

Participants with 6 to <12 years old age received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis (P): 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile in parent study and individual pharmacokinetic profile, trough and/or peak (recovery) values; Individualized P: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized P: included addition of prevention doses prior to strenuous activity; targeting FIX trough level of > 5%, if warranted by bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such regimen. Participants who reached age of 12 during study could also choose to switch to episodic treatment group, with dosing based on participants clinical condition and type and severity of bleeding event.

Participants received rFIXFc IV according to their assigned treatment regimen as follows: Weekly prophylaxis: Participants received 20 IU/kg to 100 IU/kg rFIXFc once weekly. Dose was based on participants clinical profile observed in parent study and individual pharmacokinetic profile, trough, and/or peak (recovery) values. Individualized prophylaxis: 100 IU/kg rFIXFc every 8 to 16 days or twice a month; Personalized Prophylaxis: included addition of prevention doses prior to strenuous activity; targeting a FIX trough level of > 5%, if warranted by the bleeding history and/or activity level or dosing twice a week (25 IU/kg, twice weekly, versus 50 IU/kg, once weekly) for participants who may have better control with such a regimen. Episodic (On Demand): The individual dose of rFIXFc to treat bleeding episodes was based on participants clinical condition, type and severity of the bleeding event.