Immunogenicity and Safety of Tetravalent Dengue Vaccine (TDV) Administered With a Yellow Fever Vaccine in Adults

The vaccine tested in this study is TDV. TDV with concomitant administration of yellow fever
(YF-17D) vaccine will be tested to assess immunogenicity and safety in healthy participants
in non-endemic area(s) for both dengue and YF.

The study will enroll 900 healthy participants. Participants will be randomized to 3 groups
in 1:1:1 ratio and will be administered concomitantly and sequentially. The 3 groups are:

- Group 1: YF-17D vaccine+placebo concomitantly administered on Day 1 (Month [M0]), first
dose of TDV administered on Day 90 (M3) and second dose of TDV administered on Day 180
(M6).

- Group 2: first dose of TDV+placebo concomitantly administered on Day 1 (M0), second dose
of TDV administered on Day 90 (M3) and YF-17D vaccine administered on Day 180 (M6).

- Group 3: first dose of TDV+YF-17D vaccine concomitantly administered on Day 1 (M0),
second dose of TDV administered on Day 90 (M3) and placebo administered onDay 180 (M6).

This multi-center trial will be conducted in the United States. The overall time to
participate in this study is 360 days. Participants will make multiple visits to the clinic
with a 6 months follow up including a final visit at Day 360 for a follow-up assessment.

Inclusion Criteria:

1. Is aged 18 to 60 years inclusive, at the time of randomization.

2. Is in good health at the time of entry into the trial as determined by medical
history, physical examination (including vital signs), and the clinical judgment of
the Investigator.

Exclusion Criteria:

1. Has an elevated oral temperature ≥ 38°C (100.4°F) within 3 days of the intended date
of vaccination.

2. Has contraindications, warnings and/or precautions to vaccination with the YF-17D
vaccine as specified within the product information (especially history of thymus
dysfunction).

3. Female participant who are pregnant or breastfeeding

4. Has any history of progressive or severe neurologic disorder, seizure disorder or
neuro-inflammatory disease (e.g., Guillain-Barre syndrome) or suspected
impairment/alteration of immune function.

5. Has body mass index (BMI) greater than or equal to 35 kg/m^2 (=weight in kg/[height in
meters^2]).

6. Is intent to travel to dengue or YF endemic countries during the trial period.

7. Has received any other vaccines within 14 days (for inactivated vaccines) or 28 days
(for live vaccines) prior to enrollment in this trial or who are planning to receive
any non-trial vaccine within 28 days of trial vaccine administration.

8. Has previous and planned vaccination (during the trial conduct), against any
flavivirus including dengue, YF, Japanese encephalitis (JE) or tick-borne encephalitis
viruses.

9. Has previous participation in any clinical trial of a dengue or other flavivirus
(e.g., West Nile [WN] virus) candidate vaccine, except for participants who received
placebo in those trials.

10. Has a current or previous infection with a flavivirus such as dengue, Zika, YF, JE, WN
fever, or Saint Louis encephalitis viruses and participants with a history of
prolonged (≥1 year) habitation in a dengue endemic area.