A Study to Evaluate the Pharmacokinetics, Pharmacodynamics and Safety of Vonoprazan in Adolescents With Symptomatic Gastroesophageal Reflux Disease

Inclusion Criteria: * The participant is 12 to 17 years of age, inclusive, at the time of informed consent signing and throughout study participation. * The participant has a body weight within the 5th through 95th percentile by age, inclusive, as determined by the National Center for Health Statistics. * The participant has a medical history of symptoms of GERD for at least 3 months prior to screening, based on physical examination, current symptoms (eg, heartburn), or diagnostic tests (eg, pH or endoscopy). Notes in the medical records and/or other source documents such as prior endoscopies can be used to support the diagnosis. * The participant has symptoms of at least moderate heartburn severity based on the GERD Symptom Assessment-Investigator scale performed at screening. * The participant must be able to swallow study drug. * Parent or legal guardian (ie, legally authorized representative \[LAR\]) is willing and able to complete the informed consent process and comply with study procedures and visit schedule. The participant will provide assent as applicable. * A female participant of childbearing potential who is or may be sexually active with a nonsterilized male partner agrees to routinely use adequate contraception from the signing of informed consent until 2 weeks after the last dose of study drug. Exclusion Criteria: * The participant has used prescription or non-prescription proton pump inhibitors (PPIs) or histamine-2 receptor antagonists (H2RAs) within 7 days prior to randomization or requires their use during the Treatment Period. * The participant has used sucralfate or antacids within 1 day prior to randomization or requires their use during the Treatment Period. * The participant has received other agents affecting digestive organs, including muscarinic antagonists (eg, hyoscyamine), prokinetics, oral anticholinergic agents, prostaglandins, bismuth from 30 days prior to Day 1 or requires their use during the course of the study. * The participant has received atazanavir sulfate or rilpivirine hydrochloride from 5 days prior to Day 1 or requires their use during the course of the study. * The participant has received any investigational compound (including vonoprazan) within 30 days prior to the start of the Screening Period. * The participant is an immediate family member or is in a dependent relationship with a study site employee who is involved in the conduct of this study (eg, child, sibling) or who may have consented under duress. * The participant requires hospitalization or has surgery scheduled during the course of the study or has undergone major surgical procedures within 30 days prior to the Screening Period. * The participant has undergone prior gastrointestinal surgeries such as fundoplication. * The participant has any abnormal laboratory test values at the start of the Screening Period. * The participant has a history of hypersensitivity or allergies to vonoprazan (including the formulation excipients: D-mannitol, microcrystalline cellulose, hydroxypropyl cellulose, fumaric acid, croscarmellose sodium, magnesium stearate, hypromellose, macrogol 8000, and titanium oxide, or red or yellow ferric oxide). * The participant used any prescription (excluding hormonal birth control) or over-the-counter medications (including CYP3A4 inducers), including herbal or nutritional supplements, within 14 days (or 5 half-lives) before the first dose of study drug or throughout the study. NOTE: Acid suppressive therapies are considered separately under exclusion criteria 1 and 2. * The participant has consumed grapefruit or grapefruit juice, Seville orange or Seville orange-containing products (eg, marmalade), or other food products that may be CYP3A4 inhibitors (eg, vegetables from the mustard green family \[kale, broccoli, watercress, collard greens, kohlrabi, Brussels sprouts, mustard\] and charbroiled meats) within 7 days (or 5 half-lives) before the first dose of study drug or throughout the study. * Female participant has a positive pregnancy test at screening or check in or is lactating. * The participant has a positive urine drug or alcohol result at screening. * The participant has positive results at screening for human immunodeficiency virus, hepatitis B surface antigen, or hepatitis C virus. * In the opinion of the investigator, the participant is not suitable for entry into the study.