The Dengue Vaccine

Many Canadians travel to areas in the world where dengue fever is a risk. We are often asked at TravelSafe about the dengue fever vaccine in our clinic. Here’s everything you need to know about dengue fever and the vaccine to prevent it.

What is dengue fever and how is it spread?

Dengue fever is a virus spread through the bite of an infected mosquito. The virus is spread by the Aaedes species of mosquito which mainly bites during daytime hours. Peak biting times are the first 2-3 hours after dawn, and mid-to-late afternoon (although risk can be continuous indoors or during overcast days). Dengue can also be transmitted through a blood transfusion, from mother to fetus during pregnancy, or to an infant through breast milk.

There are 4 types of the dengue virus. Someone who recovers from one of the 4 types of dengue will have lifelong immunity against that type but can still be susceptible to getting one of the other 3 types. A person is at higher risk of severe illness from dengue if they get infected with the virus a second time.

Where is dengue a risk?

Dengue is a risk in more than 100 countries worldwide, causing an estimated 50 million cases per year. Dengue is widespread across most tropical and subtropical countries of Asia, the Caribbean, the Americas, South Pacific, East and West Africa, and the Indian Ocean islands. It is largely a risk in highly populated urban areas as the Aedes aegypti mosquitos prefer to rest indoors in close contact with humans. Dengue is the most common cause of fever in travellers returning from Southeast Asia, the Caribbean, and Central America.

What are the symptoms?

Most dengue infections (around 75%) do not cause symptoms. If symptoms occur, they usually begin 2-5 days after infection. Symptoms include sudden high fever typically lasting 2-7 days, rash, muscle, abdominal, joint and back pain, headache, pain behind the eyes, nausea, vomiting and weakness. Dengue is often referred to as “breakbone fever” because of the severe joint and muscle pain it can cause. Most people improve but more severe symptoms can then develop including persistent vomiting, severe abdominal pain, bleeding from the gums, difficulty breathing, and signs of shock which can potentially be fatal. This is known as dengue hemorrhagic fever and is more common if a person gets infected with dengue a second time.

 

What is the treatment?

There is no specific treatment for dengue. It is important to stay well hydrated and avoid aspirin containing medications, and non-steroidal anti-inflammatories (i.e. ibuprofen) because of their anticoagulant properties. Fever can be treated with acetaminophen. Avoid mosquitoes to reduce dengue from further spreading. Severe dengue will require hospitalization.

 

The dengue vaccine

There is no dengue vaccine available for Canadian travellers. A dengue vaccine called Dengvaxia has been approved in certain high-risk countries for persons 9-45 years of age who have had a previous infection with dengue. Dengvaxia has been approved in the USA beginning in 2022 for children and adolescents 9-16 years of age who have laboratory confirmed previous dengue infection and are living in a US territory where dengue is endemic.

The Dengvaxia vaccine must only be given to people who have laboratory confirmation of a previous dengue infection through a blood test. If the vaccine is given to someone who has not had a previous dengue infection it increases the risk of severe illness and hospitalization. Travellers going to countries where Dengvaxia is available should avoid the vaccine unless they have reliable laboratory confirmation of a previous dengue infection.

There are 5 additional dengue vaccines in clinical development. Two of them are in Phase III trials and appear to be promising vaccine candidates in offering protection against dengue for people who have not had a previous dengue infection, including travellers.

How can I prevent dengue?

As there is no vaccine against dengue for travellers, the best way to prevent dengue is to avoid being bitten by mosquitoes:

• Stay in accommodation with air conditioning or well-screened windows and doors.
• Wear light-coloured long sleeves and pants, especially during peak biting times.
• Apply insect repellent with 30% DEET or 20% Icaridin onto exposed areas of skin.

Hopefully, all your dengue related questions have now been answered and you now have the knowledge to avoid getting dengue fever on your travels!