The enrolled population will include both, virologically-confirmed (VC) dengue cases and subjects not having experienced a VC dengue infection (control subjects) from the first Proof of Concept efficacy study conducted in Thailand Analyses for correlates will be performed on samples collected in the context of the first proof of concept efficacy study. Sequencing of dengue viruses will also be done on samples collected within the same context. Immunogenetic testing will be performed on saliva samples collected at the study enrollment visit.