Qdenga - A Promising Dengue Fever Vaccine

Dengue fever is transmitted through mosquito bites, and while mosquito control remains essential, vaccination offers an additional layer of protection. The World Health Organization (WHO) classifies dengue as one of the top 10 global health threats, with cases increasing tenfold from 500,000 in 2000 to over five million in 2019. In 2023 saw an unprecedented surge in dengue cases, with the first-ever global figures exceeding 6.5 million cases and over 6,800 deaths.Cases were reported in over 80 countries across Africa, the Americas, South-East Asia, the Western Pacific, and the Eastern Mediterranean regions. Asia recorded the highest case fatality ratio in 2023. In that year Bangladesh experienced its deadliest dengue outbreak in two decades, with 1,705 deaths out of 321,179 confirmed cases, a fatality rate of 0.53%.

In addition, spatial and temporal shifts in dengue patterns were observed in 2022 and continued in 2023. Nepal and Bangladesh experienced spikes in case numbers earlier than usual. Cases in Nepal shifted from the Kathmandu Valley in 2022 to the southeast Terai region and hill districts in Gandaki province in 2023. India, in 2023, experienced an increase in cases in Kerala and northeastern States bordering Bangladesh compared to the previous year. Vietnam has experienced dengue fever peaks approximately every 10 years between 1980 and 2018. However, the period from 2019 to 2023 saw two epidemic peaks in 2019 and 2022. In 2022, Vietnam reported over 367,000 dengue cases, second only to Brazil globally. WHO estimates about 390 million dengue infections occur worldwide annually, with 96 million symptomatic cases, 500,000 hospitalizations, and 40,000 deaths.

Vulnerable Populations and Treatment

Anyone can contract dengue fever, but children, pregnant women, and individuals with chronic diseases or obesity are at higher risk. Untreated dengue can lead to severe complications, including hypotension, heart failure, kidney failure, hemorrhagic shock, multiple organ failure, cerebral hemorrhage, and coma. Currently, treatment focuses on managing symptoms through blood filtration, plasma exchange, and anti-shock measures. The cost of treating a severe case can cross the economic ability of most of the people.

The approved dengue vaccines are Dengvaxia® and Qdenga® (TAK-003), with varying efficacies and recommended populations. Dengvaxia® has an efficacy of approximately 60–80% for preventing symptomatic dengue, but it is restricted to children aged 9-16 with a confirmed prior dengue infection due to an increased risk of severe disease in seronegative individuals. On the other hand Qdenga® shows higher overall efficacy, with around 80% protection against symptomatic dengue in both seropositive and seronegative individuals aged 4 and older.

Qdenga was invented by Takeda Pharmaceuticals, a Japanese company that developed the live, attenuated dengue vaccine (TAK-003) to protect against all four dengue virus serotypes. Regulatory bodies that approved Qdenga include the European Medicines Agency (EMA) and the European Commission (EC) in 2022, followed by other countries like Indonesia, Great Britain, Brazil, and Argentina.

As of September 2025, QDENGA was authorized in 40 countries and available in 27 countries, including Indonesia (approved Aug 2022, available April 2023), Brazil (approved Mar 2023, available June 2023, Thailand (approved May 2023, available Aug 2023), Argentina (approved Apr 2023, available Oct 2023), (approved February 2024), and is also available in Vietnam.

Efficacy and Impact of Qdenga

The Qdenga vaccine has demonstrated an efficacy of up to 80% in protecting against all four dengue virus types. More importantly, it reduces the risk of hospitalization by up to 90%. This is particularly crucial in different countries like Bangladesh, where a significant portion of the population has been infected with dengue fever at least once. Subsequent infections tend to be more severe, making timely vaccination a vital preventive measure.

A vigorous consultation with all concern stakeholders early engagement with Takeda to secure a substantial supply of the vaccine may emphasis the commitment to reducing the annual burden of dengue fever.

Our people are frequent travelers to dengue-endemic areas and there is already a demand and questions on how and when to use the vaccine. Therefore, the Vaccine Expert group of the Swedish Society for Infectious Diseases Physicians have reviewed the literature to guide and formulate recommendations on the use of Qdenga® as a travel vaccine.

•           For travelers with previous known self-reported (hospitalized or policlinic testing) dengue fever, vaccination is recommended before travel to an endemic country.

•           For dengue naïve travelers vaccination may be considered in individuals aged 4–16 years old irrespective of travel duration.

•           For travelers aged 17–60 years old are recommended considering vaccination only for longer trips and related to travel destination. They also have suggested a trip for more than six weeks to South-East Asia, a region with among the highest global incidence of dengue fever, to be used as a reference.

•           Since Qdenga® has not yet been studied in individuals >60 years old, they clearly advise vaccination should be avoided in this group until data are available.

Travelling after only one vaccine dose should be avoided if possible, which is a challenge for most travelers coming with shorter notice for travel medicine advice. It can be considered, especially in individuals with previous dengue fever, given that they receive the second dose after return. As far as we know these recommendations are more cautious than in other non-endemic countries, especially regarding the upper age limit, and should be continuously revised when more information and experience become available. For safely travelling and living, management of aedes mosquitoes along with vaccination is essential.

The writer is professor and head, Department of Entomology, National Institute of Preventive and Social Medicine, NIPSOM, Mohakhali, Dhaka. This article was originally published on Daily Sun.

BP/ZE