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A global crew of researchers has demonstrated that the tetravalent dengue vaccine often called Qdenga offered vital safety towards the illness underneath real-world situations, through the massive 2024 epidemic in São Paulo, Brazil.
The examine is printed in The Lancet Infectious Ailments and was led by Dr. Otavio Ranzani, head of the DataHealth Lab group on the Sant Pau Analysis Institute (IR Sant Pau) along with Dr. Julio Croda of Fiocruz, Brazil. It offers the primary proof of the vaccine’s effectiveness after its approval.
Dengue is likely one of the fastest-growing mosquito-borne viral ailments worldwide, fueled by local weather change and the unfold of the Aedes mosquito. Annually it causes thousands and thousands of infections in tropical and subtropical areas, and outbreaks are more and more being detected in non-endemic areas akin to Europe. On this context, having efficient vaccines with stable real-world effectiveness information is an pressing public well being want.
A examine carried out amid an epidemic
The examine was carried out within the state of São Paulo, the epicenter of the 2024 dengue epidemic, which recorded tens of 1000’s of instances. Well being authorities determined to prioritize vaccination in adolescents aged 10 to 14, since in endemic areas this age group accounts for a big proportion of symptomatic instances and faces a substantial threat of hospitalization. This age vary can also be in line with the present WHO vaccination advice.
As well as, this group is very uncovered to the mosquito vector on account of their every day actions and mobility, growing the probability of an infection. On this context, an immunization marketing campaign was launched that administered almost 690,000 doses of Qdenga over the course of the yr.
The analysis crew analyzed greater than 90,000 adolescents who introduced with acute fever and underwent particular laboratory checks (NS1 antigen detection or PCR). Utilizing a design often called test-negative case-control, they in contrast the proportion of vaccinated people amongst those that examined optimistic for dengue versus those that examined damaging, permitting estimation of the real-world effectiveness of the vaccine underneath on a regular basis situations.
Outcomes confirmed that after a single dose, the vaccine decreased symptomatic dengue instances by round 50% with the primary dose and 62% with the second, and hospitalizations by 68%. Safety started 14 days after the primary dose, was maintained through the first three months, after which declined, reinforcing the significance of finishing the advisable and authorised two-dose schedule for longer-lasting safety.
“This study design allowed us to quickly and accurately evaluate the vaccine’s effectiveness amid an epidemic, using real patient data from the health care system. It is a powerful approach to generate evidence in health emergencies,” defined Dr. Ranzani.
A sturdy examine, although with some limitations
The examine has a number of strengths that reinforce the validity of its outcomes. It’s the first analysis of the Qdenga vaccine underneath real-world situations, past scientific trials, and was carried out in an distinctive context: a significant dengue epidemic in São Paulo. The massive variety of adolescents included within the evaluation enabled strong estimates of effectiveness, whereas using a test-negative case-control design decreased the danger of biases associated to well being care-seeking habits.
As well as, outcomes remained constant throughout completely different analytical strategies, offering larger confidence within the conclusions.
Nonetheless, the authors additionally famous some limitations that needs to be thought of. Vaccine protection was comparatively low, which restricted the examine’s energy to investigate effectiveness after the second dose intimately. Info on prior dengue immunity amongst adolescents was additionally unavailable. Lastly, serotype circulation through the outbreak was targeting DENV-1 and DENV-2, stopping analysis of effectiveness towards all 4 virus serotypes (DENV-1, DENV-2, DENV-3, and DENV-4).
“Although the study has some limitations, the findings consistently show that Qdenga protects against dengue and reduces the risk of hospitalization. These data will be critical in guiding countries’ decisions on vaccination,” emphasised Dr. Ranzani.
Worldwide and European relevance
Till now, proof on the vaccine was based mostly solely on managed section 3 scientific trials. This new examine is the primary to exhibit its impression on the overall inhabitants underneath real-world situations, within the midst of a significant epidemic, reinforcing its worth for public well being decision-making.
Though Europe will not be an endemic area, the unfold of the Aedes mosquito linked to local weather change has favored the emergence of native dengue outbreaks in nations akin to France and Italy, whereas imported instances amongst vacationers proceed to rise. Catalonia is an instance of this pattern: between 2022 and 2024, greater than 500 imported dengue instances had been reported, primarily in individuals who had traveled to endemic areas. Nonetheless, episodes of native transmission have already been detected, with two instances in 2018–2019, one in 2022, and an outbreak in 2024.
“Although in Catalonia and Europe most cases are still imported, the risk of local transmission is increasing. Having effective vaccines like Qdenga can make a difference in responding to future outbreaks and protecting travelers,” stated Dr. Ranzani.
Public well being implications
The outcomes of this examine are extremely sensible. On one hand, they help using Qdenga in emergency campaigns in endemic nations, the place dengue outbreaks can rapidly overwhelm well being methods and trigger a excessive variety of hospitalizations. Proof signifies {that a} single dose already offers vital safety inside just a few weeks, making the vaccine a key instrument to curb ongoing epidemics and scale back hospital burden.
Then again, the info are additionally related for non-endemic nations, the place most instances are imported however the threat of native transmission is growing. On this context, the vaccine might play an important function in traveler prophylaxis and in stopping autochthonous outbreaks, strengthening well being system preparedness towards the unfold of the Aedes mosquito.
“The message is clear: The vaccine works and can protect against both mild and severe dengue. But to ensure sustained protection, we must complete the vaccination schedule. Our results can help policymakers and regulatory agencies better plan vaccination strategies,” added Dr. Ranzani.
Extra data:
Otavio T Ranzani et al, Effectiveness of the TAK-003 dengue vaccine in adolescents through the 2024 outbreak in São Paulo, Brazil: a test-negative, case–management examine, The Lancet Infectious Ailments (2025). DOI: 10.1016/s1473-3099(25)00382-2
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Dengue vaccine reveals effectiveness underneath real-world situations throughout Brazil’s 2024 outbreak (2025, October 1)
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