Dengue is a mosquito-borne viral infection causing a severe flu-like illness and, occasionally, a potentially lethal complication called severe dengue. The virus is primarily transmitted by
Aedes mosquitoes, particularly Aedes aegypti.
Dengue is prevalent in tropical and subtropical regions around the world, significantly impacting public health.
Why is a Dengue Vaccine Needed?
Dengue poses a significant burden on global health, with an estimated 390 million infections annually. Currently, there is no specific treatment for dengue, which makes vaccination an essential strategy for prevention. The development of an effective
dengue vaccine is crucial to reducing morbidity and mortality associated with the disease and lessening the overall health care burden.
What Challenges Exist in Developing a Dengue Vaccine?
Developing a vaccine for dengue is challenging due to the presence of four distinct
dengue virus serotypes (DENV-1, DENV-2, DENV-3, and DENV-4). Immunity to one serotype does not confer immunity to the others, and subsequent infection with a different serotype can increase the risk of severe dengue. This phenomenon is known as
antibody-dependent enhancement (ADE). Therefore, a successful vaccine must provide balanced and long-lasting protection against all four serotypes.
What Dengue Vaccines Are Available?
The first licensed dengue vaccine is
Dengvaxia (CYD-TDV), developed by Sanofi Pasteur. It is a live attenuated vaccine recommended primarily for individuals aged 9 to 45 years who have had a prior dengue infection, as determined by serological testing. The use of Dengvaxia in seronegative individuals can result in an increased risk of severe dengue upon subsequent infection.
Who Should Receive the Dengue Vaccine?
The
World Health Organization (WHO) recommends the use of Dengvaxia only in individuals with a confirmed past dengue infection in endemic areas. This recommendation is based on evidence that the vaccine is more effective and safer in those who have been previously infected. Ongoing research aims to develop vaccines that are safe and effective for seronegative individuals.
What Are the Benefits and Risks Associated with Dengvaxia?
Dengvaxia has been shown to reduce dengue cases and hospitalizations among those who have had a prior dengue infection. However, the risk of severe dengue in seronegative individuals has led to restrictions in its use. It is crucial that vaccination programs are accompanied by robust screening methods to ensure the vaccine is administered to the appropriate population.
What Are the Future Directions for Dengue Vaccines?
Researchers are actively working on new vaccine candidates that aim to overcome the limitations of current options. These candidates include live attenuated, inactivated, and recombinant vaccines, with some in various stages of clinical trials. The goal is to develop a
universal dengue vaccine that is safe and effective for all populations, regardless of prior exposure.
Conclusion
Dengue continues to be a significant public health challenge, and the development of effective vaccines is a key component in the fight against this disease. While Dengvaxia represents a significant step forward, its limitations highlight the need for continued research and innovation in the field of dengue vaccination. By addressing the challenges of serotype diversity and ADE, future vaccines hold the promise of providing broader protection and reducing the global burden of dengue.
