The main aim of this study is to collect more information on the effectiveness of TDV when used in a pilot public vaccination program for children and adolescents participating in a community-based cohort in Southeast Asian countries with high dengue transmission, specifically Thailand, Indonesia, and Malaysia where TDV is already approved for use.

The study will include cohort participants (individual follow-up of 3 years) who may or may not later be vaccinated with TDV as part of a pilot public vaccination program in the study countries. The study will investigate if cohort participants who were vaccinated with TDV have less hospital stays due to dengue than cohort participants who were not vaccinated with TDV. The study will also provide further information on the effectiveness of TDV against the least common dengue virus serotypes (DENV-3 and DENV-4).

Inclusion Criteria:

Cohort:

To be eligible for inclusion in the study cohort, participants must meet the following inclusion criteria:

1. The participant is a child or adolescent eligible to be vaccinated with TDV as part of a vaccination program planned in the study area.
2. The participant's family do not intend to migrate away from the cohort hospital catchment area within 3 years of his/her enrollment into the study cohort.
3. The participant's parent(s) or legally acceptable representative (LAR) signs and dates a written informed consent form (ICF), and any required privacy authorization where applicable, prior to the initiation of any study procedures, after the nature of the study has been explained according to local regulatory requirements.
4. The participant signs and dates an age-appropriate assent form prior to the initiation of any study procedures, after the nature of the study has been explained according to local regulatory requirements.
5. The participant's parent(s) or LAR agrees that a baseline blood sample may be taken from the participant.

Cases:

To be eligible for inclusion as a case, participants must meet the following inclusion criteria:

1. The participant is part of the cohort.
2. The participant is hospitalized and clinically diagnosed with dengue.
3. The participant has a blood sample available that was taken preferably within 5 days of fever onset and/or onset of symptoms compatible with dengue.
4. The participant tested positive for dengue by RT-PCR.

Controls:

To be eligible for inclusion as a matched control, participants must meet the following inclusion criteria:

1. The participant is part of the cohort.
2. The participant had not been hospitalized with VCD at any point between enrollment in the cohort and the index date (that is, when his/her matched case was hospitalized with CDD).
3. The participant is a resident in the same neighbourhood as the matched case.
4. The participant's date of birth is in the same calendar year as the matched case.

Exclusion Criteria

Cases:

To be eligible for inclusion as a case participants must not meet any of the following criteria:

1. The participant has been vaccinated with TDV, a tetravalent, live attenuated, chimeric dengue vaccine in a yellow fever 17D backbone (CYD-TDV), or an investigational dengue vaccine prior to cohort enrollment.
2. Contraindications as per the locally approved label/product information leaflet.

Controls:

To be eligible for inclusion as a control participants must not meet any of the following criteria:

1. The participant has been vaccinated with TDV, CYD-TDV, or an investigational dengue vaccine prior to cohort enrollment.
2. Contraindications as per the locally approved label/product information leaflet.
3. The participant could not be contacted at the time of being selected as a control.

Pediatric and/or adolescent residents in the study area who are age-eligible for vaccination with TDV as part of a pilot public vaccination program (children 7-10 years in Thailand, 6-10 years in Indonesia, and 7-12 years in Malaysia).

Takeda provides access to the de-identified individual participant data (IPD) for eligible studies to aid qualified researchers in addressing legitimate scientific objectives (Takeda's data sharing commitment is available on https://clinicaltrials.takeda.com/takedas-commitment?commitment=5). These IPDs will be provided in a secure research environment following approval of a data sharing request, and under the terms of a data sharing agreement.

IPD from eligible studies will be shared with qualified researchers according to the criteria and process described on https://vivli.org/ourmember/takeda/. For approved requests, the researchers will be provided access to anonymized data (to respect patient privacy in line with applicable laws and regulations) and with information necessary to address the research objectives under the terms of a data sharing agreement.