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Dengue is one of the most common vector-borne viral diseases today, with ongoing outbreaks in Asia and Latin America. Its spread to North America highlights its global significance, as climate change and global warming increase the likelihood of its expansion into previously unaffected regions.

With the development and availability of new vaccines, policymakers must determine which are most suitable for at-risk populations. This session, presented at the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) 2025 in Vienna, Austria, explored the geographic distribution, clinical presentation, treatment algorithms, and potential use of current dengue vaccines.

In Brazil, dengue follows a seasonal pattern, peaking during the rainy season from October to May. Most cases occur in adults aged 20-59 years, with deaths primarily affecting individuals with comorbidities or those older than 60 years. Since 2010, all four serotypes have been circulating, but dengue virus (DENV) serotypes 1 (DENV-1) and 2 (DENV-2) have been most common recently.

However, 2024 has seen an unprecedented epidemic in terms of both case numbers and duration. Changes in dominant serotypes are believed to contribute to the surge in infections and shifts in disease severity.

In this context, controlling the dengue epidemic means reducing infectivity and protecting vulnerable individuals. Since mosquito vector control is complex and no specific treatment for dengue exists, vaccines are the key preventive tool. Expanding vaccine availability and including travelers in the susceptible population are crucial steps.

The speaker’s team at this conference, from the Butantan Institute in São Paulo, Brazil, has been involved in the development of one of these vaccines. It is a tetravalent live-attenuated vaccine that covers all four dengue serotypes. The vaccine originated from the Laboratory of Infectious Diseases at the US National Institutes of Health, which licensed it to interested partners for further development. In 2018, Merck Sharp & Dohme Pharmaceuticals Ltd. and the Butantan Institute began a collaboration to advance the vaccine.

The ongoing phase 3 trial is a single-dose, placebo-controlled study that has enrolled more than 16,000 participants, who will be followed for a total of 5 years. The primary goal is to assess efficacy through polymerase chain reaction diagnosis of symptomatic dengue cases and to monitor for any potential vaccine-related adverse effects.

An interim analysis was conducted after 2 years of follow-up. Data are presented for DENV-1 and DENV-2, as these were the most prevalent during the latest epidemic, with no cases of DENV serotypes 3 or 4 detected during the study period.

• When considering DENV-1 and DENV-2 together, without differentiating participants’ serological status, the vaccine’s efficacy was 79.6%. After adjusting for prior dengue infection, efficacy increased to 89.2% compared with 73.6% in seronegative individuals.
• For DENV-1, without adjusting for serostatus, efficacy was 89.5%, reaching 96.8% in participants with prior dengue exposure and dropping to 85.6% in those without prior exposure.
• For DENV-2, without adjusting for serostatus, efficacy was 69.6%, rising to 83.7% in participants with prior dengue exposure and falling to 57.9% in those without prior exposure.
• Systemic adverse effects were common (58%), though severe reactions were rare. Their frequency increased with age. The most reported adverse effects included headache, rash, and itching across all age groups, while the most frequent local reaction was pain at the injection site.

One of the vaccine’s key advantages is that it requires only a single dose, making it ideal for outbreak situations and enabling a rapid response. Although it is pending approval by the Brazilian government, it is expected to begin administration this year. It will take at least 5 years to produce enough doses to vaccinate the entire country.

This story was translated from Univadis Spain using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.