Even one Dengvaxia dose offered lasting protection against severe dengue

Cebu children received only one dose after the 2017 vaccination program was halted.

A single dose of Dengvaxia showed lasting protection against more severe forms of dengue among children in Cebu, according to a 2025 study.

The study was published in the medical journal Vaccine in April 2025. The UP Office of the Vice President for Academic Affairs featured it in a blog post on Aug. 25.

Researchers found that one dose was associated with 21% protection against dengue-related hospitalization and 31% protection against dengue with warning signs and severe dengue. The 21% estimate was not statistically significant, while the 31% estimate was.

The finding is notable because Dengvaxia was designed as a three-dose vaccine. In 2017, the Department of Health began giving it to children aged 9 to 14 in Cebu. But the program was halted after its manufacturer, Sanofi Pasteur, disclosed that the vaccine could increase the risk of severe dengue among people who had never previously been infected.

The disclosure triggered widespread fear around Dengvaxia and vaccination in the Philippines. A later National Institutes of Health study found that media hype, false narratives on social media, politicized congressional inquiries, and unsubstantiated claims contributed to mass hysteria. The halted program left many children with only one dose.

Researchers followed eligible children in Cebu from 2018 to 2023 who were later hospitalized with suspected dengue. Blood tests confirmed the infections, and researchers compared vaccinated children with unvaccinated peers. Of 584 confirmed cases, nearly 68% had warning signs, eight developed severe dengue, and one died.

Protection was strongest in the first year, when the vaccine was 49% effective against hospitalization, but weakened over time. Protection against more severe dengue also fell from 51% in an earlier analysis to 31% in the longer study, which researchers said likely reflected the vaccine’s waning effect.

The researchers also stressed that Dengvaxia’s effectiveness depends on whether a person had previously been infected with dengue. However, the study could not establish each child’s dengue exposure before vaccination, limiting comparisons with earlier trials.

The controversy may have also affected the study’s estimates. Researchers said families of vaccinated children may have been more likely to seek hospital care when they developed dengue, while those of unvaccinated children with milder symptoms may have been less likely to seek treatment because of travel costs, lost income, and other expenses.

The findings don’t mean one dose is enough. Researchers originally intended to study the full three-dose regimen, but the 2017 suspension made that impossible. Previous clinical trials have shown stronger protection against severe dengue and hospitalization with the complete regimen.

Dengvaxia is no longer available in the Philippines. The Food and Drug Administration revoked its local registration in 2019 over alleged failures to comply with post-marketing requirements. Sanofi halted global production in 2024 amid declining demand.

The dengue vaccine landscape has since moved on. Japan’s Takeda developed Qdenga, a newer dengue vaccine approved in more than 40 countries, including Indonesia, Malaysia, Vietnam, and Thailand. It has yet to receive Philippine regulatory approval.

Still, the Cebu study provides rare real-world evidence that even an incomplete Dengvaxia regimen retained some protection against more severe dengue years after vaccination.

The researchers said the findings could help inform future vaccination strategies, while the waning protection underscores the importance of completing the recommended vaccination schedule.

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