Dengue Effectiveness Study in the Philippines

Inclusion Criteria: CASE-CONTROL STUDIES * For a suspected case to be enrolled in the study, he/she should: * Provide signed informed consent and assent (as applicable) * Be within the age group eligible to receive the dengue vaccine at the time of mass vaccination (i.e. no condition that would have made him/her ineligible for dengue vaccination) * Be admitted in any of the participating hospitals for suspected dengue * Have ≤5 days history of fever. * For the case to be included in the analysis, the participant must meet all the inclusion criteria above plus have virologically-confirmed dengue infection by RT-PCR * For controls to be recruited into the study, he/she should: * Provide signed informed consent and assent (as applicable) * Be age and sex-matched to the case * Be from the same community as the matched case * Be eligible to have received dengue vaccine during the community-based dengue immunization campaign in 2017 (i.e. no condition that would have made him/her ineligible for dengue vaccination) * Have had no episode of clinically-diagnosed or laboratory-confirmed dengue fever from the start of the community -based dengue immunization campaign to the focal time (the date of onset of dengue fever in the matched case) * Should not have been previously recruited as a control. Exclusion Criteria: • Any subject whose parent/guardian refuse to provide informed consent and/or assent. * In addition, the following conditions automatically exclude children from the dengue mass immunization: * Children \<9 years or adults older than 45 years of age * Anyone who is allergic or has had an allergic reaction to a prior dose or to any component of the dengue vaccine * Recipient of blood product in the last 3 months * Immunocompromised individuals, due to but not limited to genetic defects, HIV infection, or therapies that affect the immune system such as high-dose corticosteroids or chemotherapy * Recipient of any vaccine within the past month * History of bleeding disorder * Pregnant or breastfeeding women * Enrolled in dengue vaccine Phase 3 clinical study