No serious adverse events across nearly 1,900 doses administered
As dengue fever extends its reach across more than a hundred countries and climate change widens the territory of its mosquito carriers, the question of how to protect travelers venturing into endemic regions has grown more urgent. A study conducted in Catalonia across 2024 offers a measured answer: TAK-003, Europe's first authorized dengue vaccine, demonstrated no serious adverse events across nearly 1,900 administered doses in over a thousand adults, with reactions that were mostly mild, temporary, and less pronounced after the second dose. The findings, published in The Lancet Regional Health Europe, provide the kind of safety evidence that travel medicine has lacked for non-endemic populations—older adults, those with chronic conditions, and those receiving multiple vaccines at once—and suggest that protection against dengue can now be woven more confidently into the pre-travel consultation.
- Dengue now threatens more than half the world's population, yet travelers from non-endemic regions like Europe have had little reliable data on how the only authorized vaccine performs in people like them.
- Across 1,851 doses given to 1,028 Catalonian travelers, not a single serious adverse event was recorded—a result that cuts through earlier uncertainty about the vaccine's tolerability in diverse patient groups.
- Women and those with prior dengue infection reported higher rates of reactions, and co-administration with yellow fever vaccine raised adverse event rates, but all effects remained mild to moderate and self-limiting.
- Crucially, older adults and people with pre-existing conditions showed no elevated risk, dismantling a key concern that had clouded the vaccine's rollout for these groups.
- The practical implication is significant: TAK-003 can be safely given alongside non-flaviviral vaccines in a single pre-travel visit, removing a logistical barrier that had dampened uptake.
- Researchers are calling for continued long-term monitoring, but the current evidence positions TAK-003 as a viable and well-tolerated tool as dengue's global footprint keeps expanding.
A study tracking more than a thousand adults vaccinated against dengue in Catalonia throughout 2024 has delivered reassuring news for travel medicine: TAK-003, the first dengue vaccine authorized in Europe, showed no serious adverse events across nearly 1,900 administered doses. The research, conducted by the Barcelona Institute for Global Health in collaboration with Hospital Clínic Barcelona and published in The Lancet Regional Health Europe, was designed to address a genuine gap—safety data for non-endemic populations, including older adults and people with chronic conditions, had been scarce since the vaccine's arrival.
Dengue is no longer a distant concern. Spread by Aedes mosquitoes, it now circulates in more than 100 countries, and climate change has steadily expanded the range of its vectors while international travel accelerates the virus's movement. For travelers heading into endemic zones, fever from dengue has become one of the most common medical complaints—making a reliable, well-tolerated vaccine a practical necessity rather than a luxury.
More than half of study participants reported some reaction after vaccination, but the overwhelming majority were mild or moderate: injection-site pain, headache, fatigue, and malaise—reactions familiar from many other vaccines. Notably, these effects were less common after the second dose. Women experienced more localized reactions than men, and those with prior dengue infection reported more systemic symptoms, particularly fever. Co-administration with yellow fever vaccine also raised adverse event rates. Yet none of these patterns pointed to serious risk.
Perhaps the most consequential finding for clinical practice was that people over 60 and those with pre-existing medical conditions showed no increased reactogenicity—easing a concern that had complicated recommendations for these groups. Equally useful is the confirmation that TAK-003 can be administered alongside non-flaviviral vaccines in a single pre-travel visit, sparing travelers the inconvenience of multiple appointments and potentially improving vaccination rates. The Barcelona team calls for continued monitoring of long-term effects, but their work meaningfully strengthens the case for integrating dengue vaccination into routine pre-travel care across Europe.
A study of more than a thousand travelers vaccinated in Catalonia has provided reassuring evidence that TAK-003, Europe's first dengue vaccine, carries a manageable safety profile for people traveling from regions where the disease does not circulate. Researchers at the Barcelona Institute for Global Health, working with Hospital Clínic Barcelona, tracked 1,028 adults who received the vaccine between January and December of 2024, monitoring them after each of two doses for any adverse reactions. The work, published in The Lancet Regional Health Europe, found no serious adverse events across the 1,851 total doses administered—a finding that matters because dengue has become one of the most common causes of fever in travelers heading to endemic zones, and reliable vaccine safety data for non-endemic populations has been scarce.
Dengue, spread by Aedes mosquitoes, now circulates in more than 100 countries, and more than half the world's population lives in areas where infection is possible. The disease's reach has expanded in recent decades as mosquito vectors have spread—partly due to climate change—and as international travel has accelerated the virus's movement across borders. A safe vaccine is therefore not merely a convenience but a public health necessity. TAK-003 represents the first European authorization for dengue protection, yet when it arrived, evidence on how it performed in people without prior exposure to the virus remained limited, especially in older adults, those with chronic conditions, and people receiving other vaccines simultaneously.
The Catalonian study was designed to fill that gap. Researchers followed participants closely after vaccination, documenting any local or systemic reactions. More than half reported some adverse effect, but the vast majority were mild or moderate, temporary, and notably less common after the second dose. The most frequent complaints were pain at the injection site, headache, fatigue, and general malaise—the kind of reactions familiar from many other vaccines. The study found no increased risk of adverse events in people over 60 or in those with pre-existing medical conditions, a finding that contradicts earlier uncertainty about how these groups would tolerate the vaccine.
Certain populations did show higher rates of reactions. Women experienced more adverse effects than men, though these tended to be localized to the injection site. People who had previously been infected with dengue reported more systemic reactions, particularly fever. Those who received TAK-003 at the same time as other flavivirus vaccines, such as the yellow fever shot, also had elevated adverse event rates. But none of these findings suggested serious danger—only that some groups might expect more noticeable but still manageable symptoms.
The absence of serious adverse events across nearly 1,900 doses is the study's headline finding, but its secondary message may be equally important for travel medicine. The vaccine appears safe to administer alongside non-flaviviral vaccines in pre-travel consultations, meaning travelers can consolidate their immunizations in a single visit rather than spacing them out. This practical advantage could improve vaccination uptake among people preparing for trips to dengue-endemic regions. As dengue incidence continues to climb globally, and as climate change expands the geographic range of its mosquito vectors, the ability to offer travelers a well-tolerated protective vaccine becomes increasingly valuable. The Barcelona researchers note that their work expands the safety evidence base for TAK-003 in European populations and call for continued monitoring of its long-term effects and real-world effectiveness.
Notable Quotes
Our findings expand the available evidence on the safety of TAK-003 in European travelers and highlight the need to continue assessing its impact, effectiveness and long-term safety.— Jose Muñoz, ISGlobal researcher and head of the International Health Service at Hospital Clínic Barcelona
The Hearth Conversation Another angle on the story
Why does dengue vaccine safety in travelers matter so much? Isn't dengue just another tropical disease?
Dengue infects more than half the world's population in endemic zones, and it's become the leading cause of fever in travelers heading there. Without a safe vaccine, millions of people traveling for work or family have no protection. The disease is spreading faster because of climate change and global mobility.
So TAK-003 is new. What was the gap in the evidence before this study?
The vaccine had been tested in endemic populations, but we had very little data on how it performed in people from non-endemic regions—especially older adults, people with chronic illnesses, and those getting multiple vaccines at once. Those groups are exactly who travel and need protection.
And what did the study actually show?
Across nearly 1,900 doses in over a thousand travelers, there were zero serious adverse events. Most people had mild symptoms like arm pain or headache, and those reactions got less common after the second dose. The vaccine proved safe even in people over 60 and those with pre-existing conditions.
Were there any surprises—groups that did react more?
Women reported more adverse effects, though mostly localized. People with prior dengue infection had more systemic reactions like fever. And those getting the yellow fever vaccine at the same time had higher rates. But again, nothing serious—just more noticeable symptoms in certain groups.
What does this mean for someone planning a trip to a dengue zone?
It means they can get vaccinated with confidence. And practically, they can get TAK-003 alongside other travel vaccines in one visit, which makes it more likely people will actually get protected before they leave.