Takeda Pharmaceutical Co's experimental dengue vaccine was highly effective at preventing the mosquito-borne disease in a late stage study, but it failed to protect against one type of the virus in people with no prior exposure to dengue. Takeda's vaccine was 80.2% effective at preventing dengue among children and teens in the year after they got the shot, according to results of a Phase III study published in the New England Journal of Medicine on Wednesday. Sanofi's Dengvaxia - the world's first dengue vaccine - had demonstrated 59.2% overall efficacy in the first year of follow-up based on combined results from two late-stage trials. There is an urgent need for an effective dengue vaccine. The tropical disease infects nearly 400 million people a year and kills up to 25,000 people. A preliminary analysis of Takeda's vaccine suggests it may offer unbalanced protection among the four types of dengue. Experts have long been concerned that a dengue vaccine that is only partially protective could increase the risk of severe disease after exposure to a second type of the virus.