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An experimental dengue vaccine has shown promising early results in a large, multicountry trial, but critical questions remain about its effectiveness and safety. Still unclear, for example, is whether the vaccine—which had an efficacy of 80.2% in the study—might increase disease severity in some recipients, as happened with a dengue vaccine given to 1 million children in the Philippines before the problem became clear in 2017.
Dengue virus, which is transmitted to humans by mosquitoes, infects about 390 million people each year, and the disease is rapidly increasing its reach around the world. Although it typically causes flulike symptoms or none at all, severe cases can lead to hemorrhagic fever, shock, and even death. So even less-than-ideal vaccines “can still have a public health impact,” says Derek Wallace, a clinician who heads the R&D project at pharmaceutical company Takeda in Cambridge, Massachusetts.
Vaccine - Strain - Dengue - Virus - Wallace
To test their new vaccine, which is based on a weakened strain of the dengue virus, Wallace and colleagues randomly distributed it or a placebo to 20,000 children, aged 4 to 16, in eight countries across Asia and Latin America, where the disease is endemic. Twelve months after participants received their second and final dose, the researchers compared how many people in the placebo and vaccine groups developed confirmed cases of infection with any of the four different strains, or serotypes, of dengue virus.
The vaccine had 97.7% efficacy against the dengue 2 serotype, the team reports today in The New England Journal of Medicine (NEJM). That figure dropped to 73.7% for serotype 1 and 62.3% for serotype 3; there were too few infections with serotype 4 to reach any conclusions.
Participants - Infections - Vaccine - Risk - Hospitalization
In participants who had confirmed dengue infections, the vaccine reduced the risk of hospitalization by 95.4%. “The results are very encouraging,” says Jeremy Farrar, head of the Wellcome Trust biomedical charity...
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