Qdenga (TAK-003, Takeda) is the dengue vaccine available in Vietnam, licensed since May 2024. This article is based on Chapter 12 of the book Dengue fever (Vietnam Association of Preventive Medicine and Vietnam General Association of Medicine; printing sponsored by Takeda Vietnam) and Part III of the book Recommended vaccination schedules for all ages in Vietnam (Vietnam Association of Preventive Medicine, 3rd edition, 2026).

How the vaccine is made

Qdenga is a live attenuated, tetravalent vaccine. It uses the genetic backbone of a weakened dengue type 2 virus, carrying the surface protein genes of types 1, 3 and 4. So one injection contains all four virus types that cause the disease.

The previous-generation vaccine, Dengvaxia, used the genetic backbone of the yellow fever vaccine. Dengvaxia could only be used in people who had already had dengue, and Sanofi stopped producing it in January 2024.

Source: Dengue fever (Vietnam Association of Preventive Medicine and Vietnam General Association of Medicine; printing sponsored by Takeda Vietnam), Chapter 12, sections 2.1–2.2, pp. 239–242.

Who can be vaccinated and how many doses

People aged 4 years and over.
Two doses of 0.5 ml given under the skin, 3 months apart. Do not shorten this interval.
If dose 2 is late, there is no need to start again; give dose 2 as soon as possible.
No booster is currently recommended.

There is no need to test whether someone has had dengue before vaccination. This is a difference from Dengvaxia.

Source: Dengue fever (Vietnam Association of Preventive Medicine and Vietnam General Association of Medicine; printing sponsored by Takeda Vietnam), Chapter 12, pp. 244–246; Recommended vaccination schedules for all ages in Vietnam (Vietnam Association of Preventive Medicine, 3rd edition, 2026), Part III, section 13.2, p. 119.

Who should not be vaccinated

People allergic to any component of the vaccine.
People with congenital or acquired immunodeficiency.
Pregnant women.
Breastfeeding women.

Because it is a live vaccine, Qdenga is not given on the same day as other live vaccines; the two must be 28 days apart. Women planning a pregnancy should finish vaccination at least 1 month beforehand.

Source: Dengue fever (Vietnam Association of Preventive Medicine and Vietnam General Association of Medicine; printing sponsored by Takeda Vietnam), Chapter 12, p. 245; Recommended vaccination schedules for all ages in Vietnam (Vietnam Association of Preventive Medicine, 3rd edition, 2026), Part VI, sections 2.1 and 6.3, pp. 200, 205; Part IV, section 2.3, p. 182.

Effectiveness in trials

The main trial (DEN-301) included 20,099 children aged 4–16 in 8 countries in Asia and Latin America, followed for 4.5 years. Results:

In the 12 months after dose 2: 80.2% fewer cases of symptomatic dengue.
In the 18 months after dose 2: 90.4% fewer hospital admissions for dengue.
After 4.5 years: 61.2% fewer cases of symptomatic dengue and 84.1% fewer hospital admissions.
By virus type: highest against type 2 (95.1%), 69.8% against type 1. Efficacy was lower against types 3 and 4.
People who had never had dengue: 66.2% efficacy. People who had had dengue: 76.1%. No increased risk of severe disease was seen in people who had never been infected.

The vaccine does not give complete protection. After vaccination it is still necessary to get rid of mosquito larvae, prevent mosquito bites and watch for warning signs when there is a fever.

Source: Dengue fever (Vietnam Association of Preventive Medicine and Vietnam General Association of Medicine; printing sponsored by Takeda Vietnam), Chapter 12, pp. 242–246.

Reactions after vaccination

In trials with more than 22,000 people, the rate of reactions was similar to that in the placebo group. The most common were pain and swelling at the injection site, mild fever and tiredness. Reactions usually appear in the first 2 days, last 1–3 days, and are less frequent after the second dose. There were no cases of shock, severe bleeding or death caused by the vaccine.

Source: Dengue fever (Vietnam Association of Preventive Medicine and Vietnam General Association of Medicine; printing sponsored by Takeda Vietnam), Chapter 12, pp. 243, 246–247.

Who should consider vaccination

The Recommendations book includes the dengue vaccine in the schedules for children from 4 years, adolescents, people before having children, health workers and older adults. Older adults, people with chronic underlying conditions and people infected for a second time are the groups most likely to develop severe disease.

Source: Recommended vaccination schedules for all ages in Vietnam (Vietnam Association of Preventive Medicine, 3rd edition, 2026), Part II, Table 2, p. 33; Part IV, sections 2.2–2.6, pp. 179–186.