Dengue: the new vaccine and the importance of behavioral prophylaxis

Dengue is a tropical infectious disease, transmitted through the bites of mosquitoes belonging to the species Aedes aegypti and Aedes albopictus (the common tiger mosquito), mainly prevalent in tropical and sub-tropical areas, affecting both the traveler and the native. It is most often manifested by fever, headache, eye, muscle and joint pain, and vomiting that begin to occur 5-6 days after the mosquito bite. This disease may occur more rarely in a hemorrhagic form, potentially fatal.

Rates of dengue worldwide have increased dramatically in recent decades, and it is estimated that there are 100-400 million infections each year. According to the World Health Organization, regions in the Americas, Southeast Asia, and the Western Pacific are the most affected. Seasonal cases are also reported in the United States.

Continental European countries that have reported native (locally acquired) dengue cases since 2010 include Croatia, France, Italy, and Spain. The island of Madeira, Portugal, also reported cases in 2012. The tropicalization of the Mediterranean area is leaving ample room for the proliferation of mosquitoes that transmit this virus.

Generally, all travelers to areas reporting dengue cases or where dengue is believed to occur are at risk for this infection; therefore, vaccine prophylaxis with the new Qdenga vaccine is recommended for all such travelers.

Qdenga Vaccine

On 02/23/2023, AIFA authorized the use and marketing of Qdenga (Takeda), the new vaccine against all serotypes of Dengue virus. This vaccine also received approval from the EMA on 5/12/2022.

Qdenga is a vaccine consisting of attenuated viruses of all Dengue serotypes (DEN-1, DEN-2, DEN-3, and DEN-4), can be administered in all individuals who have reached the age of 4 years. The vaccination protocol involves two doses, administered at least three months apart. The most common side effects include hypersensitivity to one of the vaccine components, congenital or acquired immunodeficiencies, pregnancy, and lactation.

The most common adverse reactions, on the other hand, are:

• pain at the injection site (50%);
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• cephalea (35%);
• malgia (31%);
• erythema at the injection site (27%);
• general malaise (24%);
• asthenia (20%);
• fever (11%).

It is contraindicated for pregnant and nursing women, and it is also recommended not to remain pregnant for at least one month after administration. It can be co-administered with all vaccines, otherwise it should be spaced 4 weeks apart with other live attenuated vaccines.

Find out more about the vaccine

It is important to remember that, like any vaccine, Qdenga does not guarantee complete protection of the person to whom it is administered or in any case the immune response may wane over time. For this reason, it is always helpful to speak with a Travel Medicine specialist.

Consult a travel medicine specialist

Behavioral Prophylaxis

A combination of the measures listed below is considered the most effective way to prevent bites and stings from vectors (mosquitoes and ticks):

• Avoid areas with standing water, where mosquitoes are likely to breed;
• Maintain sidewalks and do not walk in tall grass to avoid tick bites;
• Check the entire body surface for ticks after outdoor activity and remove them promptly;
• Wear loose-fitting, long-sleeved clothes, long pants, tucked into socks;
• Light-colored clothes help see ticks and other insects; avoid dark blue clothes where the tsetse fly is present. To date, there are no scientific studies that clothing color is relevant to mosquitoes;
• Clothing can be sprayed or impregnated with insecticide (e.g., permethrin) or purchased pretreated to reduce bites through clothing. These treatments can provide a high level of bite prevention. Alternatively, DEET-based repellents can be applied to natural fibers such as cotton, but can damage synthetic fabrics;
• Use insect repellents on exposed skin (even if clothing has been treated): DEET-based repellents are considered the most effective currently available. If DEET is not tolerated (or is not available), an alternative preparation should be used (seek advice from the Travel Medicine during the Pre-Travel Medical Consultation);
• In areas with vector-borne diseases, use air conditioning where available or sleep in screened accommodations under an insecticide-impregnated mosquito net;
• For those who stay for long periods of time in areas with vector-borne diseases, you can reduce mosquito breeding sites around the house by removing any puddles of water in ditches, pots, gutters, drains, and garbage collected in the area.

Sources:

https://www.ema.europa.eu/en/documents/product-information/qdenga-epar-product-information_it.pdf

https://www.ema.europa.eu/en/documents/product-information/dengvaxia-epar-product-information_it.pdf

https://www.aifa.gov.it/documents/20142/1832952/DETERMINA_39-2023_QDENGA.pdf

https://www.epicentro.iss.it/febbre-dengue/