These results highlight the need to consider 1) dengue vaccination status when interpreting dengue serological tests, especially in dengue-endemic countries, because IgG and IgM ELISAs may not be able to differentiate between vaccination and natural infection, and 2) the relevance of using antigen- or molecular-based assays as an alternative to identify dengue infection in febrile vaccinees. Here, CD40LG is linked to dengue disease.