Inclusion Criteria:
1. Participants aged 2 to 17 years at the time of study enrollment with no prior dengue exposure (as determined by IgG ELISA), at research centers located in cities within areas of low to medium endemicity for dengue virus infection.
2. Agreement to periodic contact via telephone, electronic means, and home or research center visits.
3. Participants of reproductive potential must be using an effective contraceptive method for at least 30 days at screening and continue doing so until Day 363 post-first vaccination; exceptions apply if the participant (or their legal representative) declares the participant to be at no risk of pregnancy-whether due to sexual abstinence or engaging in non-reproductive sexual practices-through Day 363 post-first vaccination.
4. Demonstrated intention to participate in the study, documented by the signature of the informed consent form by the participant's parents and the informed assent form by the participant (where applicable), as well as agreement to study procedures, including completing participant diaries, undergoing blood sampling, and being available for scheduled study visits and contacts.
Exclusion Criteria:
1. Reactive or unavailable dengue IgG ELISA test result.
2. For female participants of reproductive potential: pregnancy (confirmed by a positive β-hCG test), breastfeeding, or expressed intention to engage in sexual practices with reproductive potential without using a contraceptive method up to Day 363 after the first vaccination;
3. Planned donation of blood, semen, or ova up to Day 363 after the first vaccination;
4. Evidence of active, uncontrolled neurological, cardiac, pulmonary, hepatic, or renal disease-defined as disease requiring a change in treatment or hospitalization due to worsening of the condition within the 90 days prior to study screening, based on medical history or physical examination, at the investigator's judgement;
5. Diseases compromising the immune system, including: decompensated diabetes mellitus; active neoplasms or a history of neoplasms within the last five years (except basal cell carcinoma); congenital or acquired immunodeficiencies (except HIV infection with undetectable viral load and CD4+ T-lymphocyte count \> 500 cells/mm³); solid organ transplantation (heart, liver, pancreas, lung, kidney); or uncontrolled autoimmune diseases (based on medical history or physical examination); as well as a history of hepatic insufficiency, heart failure, or end-stage or dialysis-dependent chronic kidney disease;
6. Behavioral, cognitive, or psychiatric condition that, in the opinion of the principal investigator or their medical representative, affects the potential participant's ability to understand and comply with the study protocol requirements;
7. Any use of alcohol or drugs considered abusive within the 12 months prior to study enrollment that has caused medical, occupational, or family problems, as indicated by clinical history;
8. History of severe allergic reaction or anaphylaxis to the study vaccine or its components;
9. History of asplenia;
10. Participation in another clinical trial involving the administration of an investigational product during the six months prior to study enrollment, or participation in another clinical trial during the 12 months following enrollment;
11. Prior participation in a clinical study of (or exposure to) any dengue vaccine;
12. Use of potent immunosuppressive therapies (excluding corticosteroids) in the six months prior to study enrollment. Potent immunosuppressive therapies are considered to include: antineoplastic chemotherapy, radiotherapy, immunosuppressants used to induce transplant tolerance, and potent monoclonal antibody therapy for the treatment of rheumatological diseases, among others;
13. Receipt of an immunosuppressive dose of corticosteroids within the three months prior to study enrollment. An immunosuppressive corticosteroid dose is defined as equivalent to a prednisone dose of 2 mg/kg/day for children and 20 mg/day for adolescents for 14 days (a cumulative equivalent dose of at least 280 mg of prednisone). Continuous use of topical or nasal corticosteroids is not considered immunosuppressive;
14. Receipt of blood components (transfusions) or blood derivatives (immunoglobulins) within the six months prior to study enrollment;
15. Any other condition that, in the opinion of the principal investigator or their medical representative, could jeopardize the safety or rights of a potential participant or prevent them from complying with this protocol.
