The survey is intended to investigate the following matters, etc. under the actual use status after marketing in all patients who are administered this drug for a certain period of time after the launch.

1. Occurrence status of adverse events
2. Factors that may influence the safety
3. Efficacy In addition, the following occurrence statuses will be investigated as priority items of the survey: Incidence rate of inhibitor, reduction in drug, efficacy, Allergic reaction, and Thrombosis.

Patients with hemophilia B (congenital blood coagulation factor IX deficiency) who are administered this drug.

Patients with hemophilia B are either patients for whom treatment was already started with a blood coagulation factor IX product ("Previously treated patients": hereinafter, "PTPs") or patients who have no history of treatment with a blood coagulation factor IX product in the past and for whom treatment will be started with this drug for the first time ("Previously untreated patients": hereinafter, "PUPs").

The definition of PUPs in this survey is "Patients in whom the total number of days of administration of a blood coagulation factor IX product other than this drug before administration of this drug was 3 exposure days (actual number of days of administration: hereinafter, "EDs") or less."

Inclusion Criteria:

• All patients with hemophilia B scheduled to receive treatment with BeneFIX will be eligible for the surveillance.
• No patient will be excluded because of prior inhibitor history; however, complete patient history and demographics will be collected.

Exclusion Criteria:

• Patients not administered BeneFIX.

Patients with hemophilia B (congenital blood coagulation factor IX deficiency) who are administered this drug.

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

A total of 314 participants completed the study. Of the 314 participants, 2 participants were excluded from the baseline analysis. One was excluded due to no information after first day of treatment and no drug administration, the other due to safety not assessable and no drug administration.

The frequency of adverse events. The same event may appear as both an adverse event and a serious adverse event. However, what is presented are distinct events. An event may be categorized as serious in one subject and as nonserious in another subject, or one subject may have experienced both a serious and nonserious event during the study.