The purpose of this study is to compare the efficacy of treatment with ustekinumab or adalimumab in biologic naive participants with moderately-to-severely active Crohn's disease (CD) who have previously failed or were intolerant to conventional therapy (corticosteroids and/or immunomodulators, such as azathioprine, 6-mercaptopurine, or methotrexate), as measured by clinical remission at one year.