Monday, September 18, 2023

Dengue Vaccine Types of Dengue Vaccines

Dengue Vaccine: Understanding Prevention and Protection

Dengue fever is a mosquito-borne viral infection that affects millions of people each year, particularly in tropical and subtropical regions of the world. It is caused by the dengue virus, which is transmitted to humans through the bites of infected Aedes mosquitoes. The disease is characterized by a sudden onset of high fever, severe joint and muscle pain, rash, and bleeding complications. In severe cases, dengue can lead to dengue hemorrhagic fever or dengue shock syndrome, which can be fatal if not treated promptly.

Given the significant public health burden posed by dengue, researchers have been working for decades to develop an effective dengue vaccine. In this article, we will explore the key aspects of dengue vaccines, including their development, types, recommendations, effectiveness, and potential side effects.

Development of Dengue Vaccines

The development of dengue vaccines began in the 1920s, but progress was slow due to the complex nature of the virus. Dengue virus has four distinct serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), and infection with one serotype does not provide immunity against the others. In fact, subsequent infections with different serotypes can lead to more severe forms of the disease.

Overcoming the challenge of developing a vaccine that provides protection against all four serotypes has been a major hurdle in dengue vaccine development. Nevertheless, several dengue vaccines have been developed and are now available.

Types of Dengue Vaccines

There are two main types of dengue vaccines currently in use:

1. Dengvaxia (CYD-TDV): Dengvaxia, developed by Sanofi Pasteur, is a live attenuated tetravalent vaccine that targets all four dengue virus serotypes. It is administered as three separate injections, with the initial dose followed by two additional shots given six and twelve months later. Dengvaxia has been approved in multiple countries, including some parts of the United States, but its use is limited to individuals who have previously been infected with dengue, as it may increase the risk of severe dengue in those without prior exposure.

2. Qdenga (TAK-003): Qdenga, developed by Takeda, is a recombinant chimeric attenuated vaccine with components from different dengue virus serotypes. Unlike Dengvaxia, it appears to be safer for use in individuals who have not been previously infected with dengue. Qdenga has received approvals in various countries, including the European Union.

Recommendations for Dengue Vaccination

The recommendations for dengue vaccination are specific and revolve around the following key factors:

1. Age: Dengue vaccines are primarily recommended for children aged 9 to 16 years old.

2. Prior Dengue Infection: Dengue vaccination is only recommended for individuals who have laboratory-confirmed evidence of a previous dengue infection. This is crucial to avoid potential complications in those without prior exposure.

3. Geographic Location: Vaccination is typically recommended for individuals living in areas where dengue is common or endemic. These regions include parts of the United States, such as American Samoa, Puerto Rico, the U.S. Virgin Islands, as well as various tropical and subtropical areas worldwide.

Special Considerations

Pregnant individuals were not specifically studied in dengue vaccine trials, so the vaccine's safety during pregnancy remains unclear. Likewise, there is limited information regarding the use of dengue vaccines during breastfeeding.

Who Should Not Get a Dengue Vaccine

Certain groups should not receive dengue vaccines. These include:

1. Children under 9 years of age: Younger children are less likely to have had a prior dengue infection, making vaccination inappropriate for them.

2. Individuals over 16 years of age: The available dengue vaccines are not licensed for use in individuals over 16 years old, as there is insufficient data on their effectiveness in this population.

3. Individuals who have not had a prior dengue infection.

4. Individuals with weakened immune systems (immunocompromised).

5. Individuals who have had a severe allergic reaction to a previous dose of the vaccine or to any of its ingredients.

Effectiveness of Dengue Vaccines

Dengue vaccines, particularly Dengvaxia, have shown effectiveness in protecting individuals who have previously had a dengue infection. Dengvaxia has been found to be approximately 80% effective in preventing symptomatic dengue illness and hospitalizations in this group.

However, it is important to note that no vaccine provides complete immunity, and there is still a low risk of "vaccine breakthrough," where some vaccinated individuals may still get infected with dengue. The duration of protection provided by the vaccine is an ongoing area of research.

Possible Side Effects

Common side effects of dengue vaccines, especially in individuals who have had dengue before, may include soreness, itchiness, or pain at the injection site, headaches, fatigue, and general discomfort. Severe allergic reactions are extremely rare.

As with any vaccine, individuals may sometimes experience fainting after vaccination. This can be prevented by sitting or lying down for about 15 minutes after receiving the vaccine.

Access to Dengue Vaccines

Dengue vaccines are typically available through healthcare providers, community health clinics, pharmacies, workplaces, health departments, and other community locations. In the United States, the Vaccines for Children (VFC) program provides vaccines for eligible children aged 18 and younger who are uninsured, underinsured, Medicaid-eligible, American Indian, or Alaska Native.

Dengue vaccines represent a significant advancement in the prevention of dengue fever, a potentially severe and life-threatening disease. While they are not without limitations and specific recommendations, they offer valuable protection to individuals living in dengue-endemic regions, especially those with prior dengue infections. The ongoing research and development of dengue vaccines aim to improve their effectiveness and accessibility, ultimately reducing the global burden of dengue.

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