Guselkumab will be administered subcutaneously.

Corticosteroid-free (90-day) clinical remission at Week 48 is defined as clinical remission at Week 48 and not receiving corticosteroids for at least 90 days prior to Week 48. Clinical remission is defined as a CDAI score of <150. CDAI scores range from 0 to approximately 600. Higher score indicates higher disease activity.

Corticosteroid-free (90-day) patient-reported outcome(s) (PRO-2) remission at Week 48 is defined as an abdominal plan (AP) mean daily score less than or equal to (<=) 1 and stool frequency (SF) mean daily score <= 2.8, and no worsening of AP or SF from baseline, and not receiving corticosteroids for at least 90 days prior to Week 48.

Sustained clinical remission is defined as clinical remission at Week 12 and Week 48. Clinical remission is defined as CDAI score of <150. CDAI scores range from 0 to approximately 600. Higher score indicates higher disease activity.

Histologic-endoscopic remission at week 48 is defined as achieving a combination of histologic remission and endoscopic remission at Week 48. Histologic remission is defined as absence of neutrophils from the mucosa (both lamina propria and epithelium), no crypt destruction, and no erosions, or ulcerations or granulation tissue as assessed by the Robarts Histopathology Index. Endoscopic remission is defined as a SES-CD score of <= 4 with at least a 2-point reduction from baseline and no subscore > 1 in any individual component.

IBDQ response at Week 48 is defined as an improvement of at least 16 points in the IBDQ total score from baseline at Week 48. IBDQ is a validated, 32-item, self-reported questionnaire for participants with IBD that will be used to evaluate disease-specific health related quality of life (HRQoL) across 4 dimensional scores: bowel symptoms (loose stools, AP), systemic function (fatigue, altered sleep pattern), social function (work attendance, need to cancel social events), and emotional function (anger, depression, irritability). Scores range from 32 to 224, with higher scores indicating better outcomes.

PROMIS-29 MCS response at Week 48 is defined as an improvement of at least 7 points in PROMIS-29 MCS score from baseline at Week 48. The PROMIS-29 is a collection of short forms containing 4 items for each of 7 domains (depression, anxiety, physical function, pain interference, fatigue, sleep disturbance, and ability to participate in social roles and activities). PROMIS-29 also includes an overall average pain intensity 0-10 numeric rating scale. The PROMIS-29 MCS will be assessed, which is primarily informed by domains of emotional distress (depression/anxiety) and fatigue as well as sleep disturbance where higher MCS scores reflect better mental health.

Clinical remission at Week 12 is defined as CDAI score <150 at Week 12. CDAI scores range from 0 to approximately 600. Higher score indicates higher disease activity.

Endoscopic response at Week 12 is defined as greater than (>) 50 percent (%) improvement from baseline in SES-CD score at Week 12 or a decrease of at least 2 points in participants with a baseline score of 4 and isolated ileal disease. SES-CD score can range from 0 to 56. Higher scores indicating more severe disease.

An AE is any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non investigational) product. An AE does not necessarily have a causal relationship with the intervention. An SAE is any untoward medical occurrence that at any dose: results in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, is a suspected transmission of any infectious agent via a medicinal product, and is medically important.