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In the wake of controversy over a Sanofi dengue vaccine, Takeda Pharmaceuticals is betting its own effort will meet a largely unmet medical need and, in the process, become a best-selling product. But preliminary results released on Wednesday suggest the company has more work to do to ensure its vaccine does not encounter the same problems that have hobbled its rival.

A key hurdle Takeda must clear is to demonstrate that its own vaccine is not hindered by an issue that has clouded Sanofi’s Dengvaxia vaccine, which can actually make future cases of the mosquito-borne virus more severe in people who were not previously infected. After this finding was disclosed two years ago, a widespread vaccination campaign run by the Philippine government was abruptly halted amid scandal. Sanofi has struggled ever since to make a success of the product.


For the moment, Takeda reported preliminary results that are decidedly mixed. When taking into account all four serotypes, or strains, of the dengue virus, the Takeda vaccine demonstrated an overall 80.2% effectiveness rate. The late-stage study, published in the New England Journal of Medicine, tested two doses in more than 19,000 children and adolescents in eight countries.

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