This study looks at how well a medicine called guselkumab works for kids with Crohn's Disease (CD). CD is a condition that causes swelling in the digestive tract. The study will last until Week 52, which means it will take about a year. The medicine will be tested on kids who show improvement by Week 12. To join, kids need to have specific symptoms of CD. These include having a diagnosis confirmed in the past and a high score on tests measuring their CD activity. They also need to have tried other CD medicines that didn’t work well for them. Kids cannot join if they have certain complications like strictures (narrowing of the intestines) or if they've had some types of surgeries recently.

• The study lasts for about 52 weeks, with important checks at Week 12.
• Participants need to have tried other CDs treatments before.
• Kids with specific CD-related problems or recent surgeries cannot join.