Dengue vaccine held up over a year in Sao Paulo adolescents, real-world study
Across 166,390 tests during Brazil's outbreak, two TAK-003 doses were 73% effective against symptomatic dengue and 88% against hospitalisation, with no sign of waning.
| Group | Value (%) |
|---|---|
| One dose | 59.2 |
| Two doses | 73.1 |
When Takeda's dengue vaccine TAK-003 was rolled out during Brazil's record outbreak, the open question was not whether it worked in a trial — that was already known — but whether it held up in the field, and for how long. A test-negative case-control study of adolescents in São Paulo State, published in EClinicalMedicine on 31 August 2026, offers a large real-world answer: the vaccine's protection lasted through a year of intense transmission, and a single dose showed no sign of fading [s1].
The setting
The study covered adolescents aged 10-15 years in São Paulo State between 20 February 2024 and 31 December 2025, spanning the 2024-2025 outbreak [s1]. The mix of circulating virus shifted over that window: DENV-1 and DENV-2 predominated in 2024, followed by rising DENV-3 transmission in 2025 — a real test of whether the vaccine's protection extends across serotypes as the epidemic evolves [s1].
That backdrop is not incidental. Dengue is escalating worldwide, and the Americas have borne much of it. WHO recorded a historic high of more than 14.6 million cases and over 12,000 dengue-related deaths globally in 2024, with the Region of the Americas contributing over 13 million of those cases [s2]. An estimated 100-400 million infections occur each year, and about half the world's population is now at risk [s2].
How it was measured
The researchers used a test-negative case-control design, a standard method for estimating real-world vaccine effectiveness [s1]. Cases were adolescents with acute febrile illness and virologically confirmed dengue — detected by NS1 antigen or RT-PCR within five days of symptom onset — while controls were test-negative febrile episodes [s1]. Individual records were drawn from the national dengue surveillance system and linked to the state vaccination registry, and effectiveness after one or two doses was estimated with mixed-effects logistic regression [s1].
The scale was substantial: 166,390 tests were analysed, comprising 65,365 from cases and 101,025 from controls [s1].
What it found
Against symptomatic, confirmed dengue, effectiveness was 59.2% (95% confidence interval 56.1-62.0) after one dose and 73.1% (69.1-76.6) after two doses [s1]. Against dengue requiring hospitalisation — the outcome that matters most for health systems — effectiveness reached 74.6% (62.7-82.7) after one dose and 87.9% (73.0-94.6) after two [s1].
The durability finding is the one that will draw attention. One-dose protection against symptomatic disease showed no evidence of waning over the year: effectiveness was 73.8% (64.7-80.6) at 270-364 days and 76.8% (59.3-86.8) at 365 days or more [s1]. Two-dose protection also remained stable to one year, at 74.6% (59.0-84.2) at 270-365 days [s1]. The results held in sensitivity analyses and were comparable during the period of increased DENV-3 circulation [s1].
Why the single-dose signal matters
The authors flag the one-dose result carefully, because of what it could mean for supply-constrained programmes [s1]. A two-dose schedule requires twice the doses, twice the visits and higher risk that people never return for the second shot. If a single dose delivers sustained protection against symptomatic disease — as this study suggests over a year — that raises a genuine hypothesis about dose reduction that, in the authors' words, warrants continued long-term observational evaluation [s1]. The point carries added weight because the same team's initial evaluation during the 2024 outbreak had shown short-term protection but suggested possible waning after 90 days of the first dose, and had limited power to estimate second-dose effectiveness against hospitalisation — exactly the uncertainties the year-long follow-up was built to resolve [s1].
They are equally clear about the limit of that idea. A second dose still provided the best protection, particularly against hospitalisation, where two-dose effectiveness of 87.9% clearly exceeded the one-dose figure [s1]. The single-dose finding is a lead to investigate, not a licence to drop the second shot.
The caveats
Test-negative studies estimate association, and the analysis relies on linked surveillance and registry data with the confounding and completeness limits those systems carry. The follow-up is one year, so it cannot speak to protection beyond that, and the population is adolescents in one Brazilian state during a specific serotype mix [s1]. Whether the same durability appears in other age groups, other settings and other serotype combinations is the open question.
What to watch
For countries deciding whether and how to deploy TAK-003 as dengue surges, this is among the larger real-world effectiveness reads to date, and it reinforces the case for vaccination as a public-health measure during outbreaks [s1]. The next chapters are longer follow-up, to see when protection eventually declines, and dedicated evaluation of whether a single dose can carry programmes where doses are scarce.
Sources
- 1-Year follow-up evaluation of TAK-003 dengue vaccine effectiveness against symptomatic disease and hospitalisation in adolescents during the 2024-2025 outbreak in São Paulo, Brazil: a test-negative case-control study — EClinicalMedicine, 31 August 2026
- Dengue and severe dengue — Fact sheet — World Health Organization
Sources
- 1-Year follow-up evaluation of TAK-003 dengue vaccine effectiveness against symptomatic disease and hospitalisation in adolescents during the 2024-2025 outbreak in Sao Paulo, Brazil: a test-negative case-control study — EClinicalMedicine , August 31, 2026
- Dengue and severe dengue — Fact sheet — World Health Organization
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