A Study to Evaluate the Efficacy, Safety, and Pharmacokinetics of Subcutaneously Administered Guselkumab for the Treatment of Chronic Plaque Psoriasis in Pediatric Participants

Prior treatment

• Has previously received guselkumab or etanercept

Other illness

• Has a history of chronic or recurrent infectious disease, including but not limited to chronic renal infection, chronic chest infection (example, bronchiectasis), recurrent urinary tract infection (recurrent pyelonephritis or chronic non-remitting cystitis), fungal infection (mucocutaneous candidiasis), or open, draining, or infected skin wounds or ulcers
• Has a known history of lymphoproliferative disease, including lymphoma; a history of monoclonal gammopathy of undetermined significance (MGUS); or signs and symptoms suggestive of possible lymphoproliferative disease, such as lymphadenopathy or splenomegaly

Lab values

• Has current drug-induced psoriasis (example, a new onset of psoriasis or an exacerbation of psoriasis from beta blockers, calcium channel blockers, or lithium)

Other

• Currently has nonplaque forms of psoriasis (example, erythrodermic, guttate, or pustular)

• Have a diagnosis of chronic plaque-type psoriasis for at least 6 months (with or without psoriatic arthritis \[PsA\]), prior to first administration of study intervention, defined as having at screening and baseline, Investigator Global Assessment (IGA) greater than or equal to (\>=) 3, Psoriasis Area and Severity Index (PASI) \>=12, \>=10% body surface area (BSA) involvement and at least one of the following: very thick lesions, clinically relevant facial, genital, or hand/ foot involvement, PASI\>=20, \>20% BSA involvement, or IGA=4
• Be a candidate for phototherapy or systemic treatment of plaque psoriasis (either naive or history of previous treatment)
• Have plaque psoriasis considered by the investigator as inadequately controlled with phototherapy and/or topical therapy after an adequate dose and duration of therapy
• Be considered, in the opinion of the investigator, a suitable candidate for etanercept therapy, according to their country's approved Enbrel product labeling
• Be otherwise healthy on the basis of physical examination, medical history, and vital signs performed at screening. Any abnormalities, must be consistent with the underlying illness in the study population and this determination must be recorded in the participant's source documents and initialed by the investigator
• Must have acceptable evidence of immunity to varicella and measles, mumps, and rubella (MMR), which includes any one of the following: documentation of age-appropriate vaccination that includes both doses of each vaccine (unless local guidelines specify otherwise) or documentation of past infection by a healthcare provider or in the absence of previous 2 criteria, participants must have positive protective antibody titers to these infection prior to the first administration of study intervention. For participants who have not completed the recommended vaccination schedule for varicella and MMR, and the subsequent vaccination falls within the next 4 years, an accelerated vaccination schedule must be completed prior to study enrollment if available and required or strongly recommended for the location. If varicella or MMR vaccines are utilized, it is necessary for 2 weeks to elapse between the vaccination and receipt of study intervention