Long-Term Safety and Antibody Persistence of TDV and the Impact of a Booster Dose

The purpose of this study is to describe antibody persistence for each of the 4 dengue serotypes for up to 63 months after the first vaccination in the primary vaccination series for participants from parent trial DEN-315 (NCT03341637) (Mexico) and for up to 36 months after the first vaccination in the primary vaccination series for participants from parent trial DEN-304 (NCT03423173) (United States \[US\]) and to describe the impact of a tetravalent dengue vaccine (TDV) booster dose vs placebo on antibody response for each of the 4 dengue serotypes at 1 month and 6 months post administration of the TDV booster or placebo.

Inclusion Criteria: 1\. Male or female participants (irrespective of serostatus at baseline in the parent trials (DEN-304 \[(NCT03423173)\] and DEN-315 \[NCT03341637\]) who received at least one dose of Takeda's tetravalent dengue vaccine candidate (TDV) in the parent trials and have data from at least one blood draw post-vaccination. Exclusion Criteria: 1. Participants with a prolonged period of habitation (≥1 year) in a dengue endemic area within the 2 years prior to Visit 1 Day 1 (Month 0). 2. Previous and planned vaccination (during the trial conduct), against any flavivirus including dengue (other than Takeda's TDV), yellow fever (YF), Japanese encephalitis (JE) viruses or tick-borne encephalitis. Booster Exclusion Criteria: 1. Participants for whom baseline serostatus is not defined in the parent trials (DEN-304 \[(NCT03423173)\] and DEN-315 \[NCT03341637\]). 2. Participants with any history of progressive or severe neurologic disorder, seizure disorder or neuro-inflammatory disease (eg, Guillain-Barré syndrome). 3. Known or suspected impairment/alteration of immune function, including: 1. Chronic use of oral steroids (equivalent to 20 mg/day prednisone ≥12 weeks/≥2 mg/kg body weight/day prednisone ≥2 weeks) within 60 days prior to Month 42 for participants from parent trial DEN-315 (Mexico)/ Month 15 for participants from parent trial DEN-304 (US); use of inhaled, intranasal, or topical corticosteroids is allowed. 2. Receipt of parenteral steroids (equivalent to 20 mg/day prednisone ≥12 weeks/≥2 mg/kg body weight/day prednisone ≥2 weeks) within 60 days prior to Month 42 for participants from parent trial DEN-315 (Mexico)/ Month 15 for participants from parent trial DEN-304 (US). 3. Administration of immunoglobulins and/or any blood products within the 3 months prior to administration of the TDV booster or placebo at Month 42 for participants from parent trial DEN-315 (Mexico)/ Month 15 for participants from parent trial DEN-304 (US); consider whether applicable as an exclusion criterion or criterion for delay. 4. Receipt of immunostimulants within 60 days prior to Month 42 for participants from parent trial DEN-315 (Mexico)/ Month 15 for participants from parent trial DEN-304 (US). 5. Immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within 6 months prior to Month 42 for participants from parent trial DEN-315 (Mexico) / Month 15 for participants from parent trial DEN-304 (US). 6. Known human immunodeficiency virus (HIV) infection or HIV-related disease. 7. Hepatitis C virus infection. 8. Genetic immunodeficiency. 4. Abnormalities of splenic or thymic function. 5. Participants with a known bleeding diathesis, or any condition that may be associated with a prolonged bleeding time. 6. Participants with history of current or previous infection with a flavivirus such as dengue, Zika, YF, JE, West Nile fever, tick-borne encephalitis or Murray Valley encephalitis and participants with a prolonged period of habitation (≥1 year) in a dengue endemic area during trial conduct.