This is an observational study in which only data are collected from participants receiving their usual treatment. The study is done in children under 2 years old with venous thromboembolism (VTE).

VTE is a condition in which blood clots form in the veins, usually in the leg. This can cause pain and swelling. The clot can also break apart and travel in the blood to the lungs where it can block the blood flow. This can be life threatening.

Rivaroxaban is approved for doctors to prescribe to children with VTE, but there is limited information about how it is used, how well it works, and how safe it is in children under 2 years old. Children in this study are already receiving or will receive rivaroxaban or other currently used medicines for VTE from their doctor according to the approved product information.

The purpose of this study is to collect information on the pattern of use and safety of rivaroxaban and other standard medicines for VTE in children under 2 years old.

The main information that researchers will collect in this study:

• Age, gender, and other information about the child and their illness
• Type of VTE treatment given to the child
• Occurrence of medically important bleeding and its severity

Further information that researchers will collect:

• Changes in the characteristics of the children given VTE treatment (e.g., changes in the age range of children given VTE treatment) and changes in the treatment pattern for VTE
• Return of VTE symptoms
• Types of doctors who prescribe VTE treatment and their set-up (e.g., special clinics versus hospitals) Besides this data collection, no further tests or examinations are needed in this study.

The data for this study will be collected from electronic health records and health insurance claims data until 2026.

Researchers will observe each child during treatment until:

• end of the anticoagulation treatment period e.g. discontinuation of all study drugs,
• their information is no longer available, or
• the study ends.

Inclusion Criteria:

• Evidence of initiation of an anticoagulant therapy (index drug), either rivaroxaban oral suspension or other anticoagulation therapies (heparins, Vitamin K antagonists (VKAs), other Direct oral anticoagulants (DOACs)). Initiation will be defined as a first record of any anticoagulation therapy (rivaroxaban or SOC) without any anticoagulation therapy in the previous 6 months, or since date of birth for children less than 6 months
• Evidence of a prior VTE diagnosis (index VTE), defined as the presence of at least one primary/main or secondary diagnosis code for VTE recorded in inpatient setting in the previous 30 days
• Age less than two years on index date.
• Baseline period for availability of patient data history in the data source. A minimal baseline period of six months before index date for children aged between six months and two years, and a baseline period since birth for children less than six months of age will be required.

Exclusion Criteria:

- None

Children aged under two years who initiate an anticoagulation therapy with rivaroxaban oral suspension or any other anticoagulation drug (index date) following a VTE diagnosis during year 2021 to 2026.

Availability of this study's data will later be determined according to Bayer's commitment to the EFPIA/PhRMA "Principles for responsible clinical trial data sharing". This pertains to scope, timepoint and process of data access. As such, Bayer commits to sharing upon request from qualified researchers patient-level clinical trial data, study-level clinical trial data, and protocols from clinical trials in patients for medicines and indications approved in the US and EU as necessary for conducting legitimate research. This applies to data on new medicines and indications that have been approved by the EU and US regulatory agencies on or after January 01, 2014.

Interested researchers can use www.vivli.org to request access to anonymized patient-level data and supporting documents from clinical studies to conduct research. Information on the Bayer criteria for listing studies and other relevant information is provided in the member section of the portal.