Dengue fever, a mosquito-borne illness, is a growing public health challenge. The virus is transmitted by infected mosquitoes and can cause symptoms ranging from a mild, flu-like illness to severe, life-threatening conditions. In response to the global spread of dengue, scientists have developed vaccines as a preventative tool. These vaccines mark a significant step in controlling the disease’s impact on populations in affected regions.
How Dengue Vaccines Work
Dengue is caused by four distinct but related virus serotypes: DENV-1, DENV-2, DENV-3, and DENV-4. Infection with one serotype provides lifelong immunity to that specific type, but only temporary protection against the others. A subsequent infection with a different serotype can lead to a more severe form of the disease. For this reason, a dengue vaccine must be “tetravalent,” meaning it is engineered to protect against all four serotypes simultaneously.
The vaccines work by introducing the immune system to a weakened or modified form of each of the four dengue viruses. This exposure is not strong enough to cause illness but is sufficient to trigger a defensive response where the immune system produces specific antibodies and memory cells. This process prepares the body to mount a rapid and effective defense if it encounters any of the four dengue serotypes in the future, preventing or reducing the severity of an infection.
Available Dengue Vaccines
Two primary vaccines have been licensed for use. The first, Dengvaxia (CYD-TDV), was developed by Sanofi Pasteur. It is a live-attenuated vaccine, which means it uses a weakened form of the live virus. Dengvaxia is constructed using a yellow fever virus backbone into which genes from the four dengue serotypes have been inserted. It has been approved in numerous countries in Latin America and Southeast Asia, and for specific populations in U.S. territories like Puerto Rico and the U.S. Virgin Islands.
A newer vaccine, Qdenga (TAK-003), was developed by Takeda. This is also a live-attenuated tetravalent vaccine, but it uses a weakened DENV-2 virus as its structural backbone to elicit a more balanced immune response. Qdenga has been approved for use in several countries, including the European Union, the United Kingdom, Brazil, and Indonesia. The World Health Organization (WHO) has also recommended its use in settings with high dengue transmission.
Who Should Get Vaccinated
Recommendations for who should receive a dengue vaccine are specific and depend on location, age, and a person’s history of dengue infection. Vaccination is recommended for individuals living in endemic areas—regions where dengue is common. This includes many tropical and subtropical areas where the mosquito vectors are prevalent.
Age restrictions are also a component of vaccination guidelines. Dengvaxia is approved for individuals aged 9 to 45 years old, while Qdenga has a broader age range from 4 or 6 up to 60 years, depending on the country. Vaccination might be considered for frequent or long-term travelers to endemic areas.
A significant factor influencing eligibility for Dengvaxia is whether a person has had a prior dengue infection. This is due to a phenomenon called Antibody-Dependent Enhancement (ADE). ADE can occur when a person who has never been infected with dengue gets vaccinated. The vaccine-induced antibodies, if unable to fully neutralize a future dengue virus, can instead help the virus enter immune cells, leading to a more severe infection.
Because of this risk, health authorities like the U.S. Centers for Disease Control and Prevention (CDC) mandate that individuals have laboratory-confirmed evidence of a past dengue infection before receiving Dengvaxia. Qdenga, due to its different design, can be administered in some regions without requiring pre-vaccination testing.
Efficacy and Safety Profile
The effectiveness of dengue vaccines is measured by their ability to prevent symptomatic illness and severe disease that leads to hospitalization. Studies have shown that Qdenga can prevent dengue fever from all serotypes at a rate of about 80.2% and is approximately 90.4% effective in preventing hospitalization. Efficacy can vary depending on the specific serotype and population, but the vaccines provide substantial protection against severe outcomes.
The safety profile for both major vaccines is favorable, with most side effects being mild and temporary. Common reactions include pain, redness, or swelling at the injection site. Some people may also experience systemic symptoms like headache, muscle pain, general malaise, or a low-grade fever. These reactions are signs that the immune system is responding to the vaccine and usually resolve within a few days.