A Study of JNJ-78934804 in Participants With Moderately to Severely Active Crohn's Disease

The purpose of this study is to assess how well JNJ-78934804 works (efficacy) and how safe it is (safety) as compared to guselkumab at Week 48 in participants with moderately to severely active Crohn's disease (a long-term, progressive \[worsens with time\] and life-threatening disease of the intestine).

Inclusion criteria: * Have a diagnosis of Crohn's disease (CD) or fistulizing CD established greater than or equal to (\>=) 12 weeks before screening including both endoscopic evidence and a histopathology report consistent with a diagnosis of CD * Have moderately to severely active CD based on crohn's disease activity index (CDAI) criteria defined as a baseline CDAI score \>= 220 but less than or equal to (\= 4.0, based on the unweighted CDAI component of the number of liquid or very soft stools or b. Mean daily AP score \>= 2.0, based on the unweighted CDAI component of abdominal pain (AP) * Have moderately to severely active ileal and/or colonic CD as assessed by central review of the screening video ileocolonoscopy based on simple endoscopic score for crohn's disease (SES-CD) criteria * Have had an inadequate initial response, loss of response, or intolerance to previously approved systemic therapies Exclusion criteria: * Diagnosis of indeterminate colitis, microscopic colitis, ischemic colitis, ulcerative colitis (UC) or clinical findings highly suggestive of UC * Complications of CD such as symptomatic bowel strictures or stenoses, or any other manifestation that may require intestinal surgery while enrolled in the study * Presence of draining (that is, functioning) stoma or ostomy * Has a history of short bowel syndrome, is missing greater than (\>) 2 of the 5 ileocolonic segments, or has any other medical condition that could preclude or confound the ability to use efficacy assessment tools (such as CDAI) to assess response to study intervention * Currently has or is suspected of having an abscess