Qdenga is a live attenuated tetravalent dengue vaccine, which means it is designed to protect against all four dengue virus strains – DEN-1, DEN-2, DEN-3, and DEN-4. Experts believe that, unlike the earlier vaccines, Qdenga works in people with or without prior dengue infection, trains the immune system to recognise and fight all dengue strains, and significantly reduces the risk of severe dengue and hospitalisation.