Dengue vaccination before travel
Dengue has moved a long way from the margins of tropical medicine. Transmission now reaches travellers across South and Southeast Asia, the Caribbean, Central and South America, parts of Africa and the Pacific, and it does not confine itself to remote areas: city stays and coastal resorts account for a good share of cases. Vaccination suits a specific group of travellers rather than all of them, and prior infection history is central to working out which group you fall into.
A daytime-biting mosquito virus
Dengue is a viral infection spread mainly by Aedes mosquitoes. These mosquitoes often bite during the day, particularly in the hours after dawn and again in the early evening. They breed close to people, including in water containers, buckets, tyres and other small collections of standing water, so dengue is common in towns and cities as well as rural areas.
Many infections cause no symptoms. When illness does appear, it can start suddenly, often with a high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting and a rash. Most people recover with supportive care, but dengue can occasionally become severe, with bleeding, abdominal pain, fluid leakage and organ problems.
A second dengue infection can carry a higher risk of severe disease than a first infection. Children, pregnant women, older adults and people with certain long-term conditions may also need more careful assessment before travelling to high-risk areas.
What Qdenga can and cannot do
The dengue vaccine available in the UK is Qdenga. It is a live attenuated vaccine, meaning it contains weakened dengue virus. It is licensed for people from 4 years of age, but UK guidance is more selective than the licence wording alone. Vaccination is generally considered for travellers aged 4 and over who have had dengue before and are going to an area with dengue risk or an active outbreak. It may also be considered for people exposed through work, such as some laboratory staff.
Exceptionally, vaccination may be discussed for someone without a clear past dengue infection, but that needs a careful risk assessment and, in some cases, further specialist advice. Previous infection may be assessed from your history and any test results, though dengue blood tests are not perfect.
The course is given as two doses, usually three months apart. Plan early if you can. Qdenga is not suitable for everyone, including people who are immunosuppressed, pregnant or breastfeeding, children under 4, or anyone with a serious allergy to a vaccine component. A booster or repeat course is not something to assume; it should be reviewed against current guidance if you remain at risk later.
Countries where dengue risk is taken seriously
Dengue occurs across tropical and subtropical regions, especially in urban and semi-urban areas. Travellers most often need dengue risk advice for destinations in South and South East Asia, such as India, Sri Lanka, Thailand, Vietnam, Indonesia and the Philippines. It is also relevant in parts of the Caribbean, Mexico, Central America, Brazil, Colombia, Peru and other parts of South America.
Risk also exists in parts of Africa, the Eastern Mediterranean and the Western Pacific. Outbreaks have been reported outside the tropics too, including parts of southern Europe, although vaccination is not usually advised for places where only sporadic local cases occur. Season, outbreak activity, length of stay and previous dengue infection all affect the advice you receive.
Bring your itinerary while there is still time
If dengue vaccination is under consideration, book while your departure date still accommodates a two-dose schedule. Useful things to bring: your itinerary and dates, any documentation of previous dengue infection or testing, and a list of your regular medicines. Some travellers leave the appointment with a vaccination plan; others leave with a considered explanation of why mosquito precautions are the better use of their time and money. Both are legitimate outcomes.