Towards a dengue vaccine: progress to date and remaining challenges.

The increased incidence and extended geographical reach of Dengue virus over the past two decades have made the development of an effective vaccine an international urgency. Various strategies are being pursued, including live, vectored and killed/recombinant preparations. For all approaches, the challenge is to induce a broad durable immune response against all four serotypes of Dengue virus simultaneously whilst avoiding the possible exacerbation of risk of developing the severe forms of disease through incomplete or modified responses. This review presents the current state of knowledge and discusses the challenges of further clinical development.