New Dengue Vaccine Shows Promising Results in Multi-country Trial
Mon, November 29, 2021

New Dengue Vaccine Shows Promising Results in Multi-country Trial

TAK-003 is the second vaccine against dengue that has been developed in the last few years. / Photo by: scyther5 via 123rf


The new vaccine against dengue showed promising results in a large, multicountry trial as initial findings demonstrate it can cut infection rates.

Developed by Japanese pharmaceutical company Takeda Pharmaceutical Co, the experimental vaccine was found to effectively protect children against one type of dengue virus. It was also found to provide good partial protection against at least two others. The Takeda vaccine is the second dengue-fighting vaccine after Dengvaxia, which was pulled out in the Philippines in 2017 due to safety concerns.

Promising Results

The multicountry trial involved 20,000 children aged 4 to 16 living in eight countries across dengue-endemic countries of Asia and Latin America. Testing the new vaccine, called TAK-003 and is based on a weakened strain of the dengue virus, required randomly distributing it or a placebo to the children.

The researchers compared the number of people n the placebo and vaccine groups that developed confirmed dengue cases with any of the four strains (serotype) of dengue virus 12 months after the participants received their second and final dose.

In their report on the New England Journal of Medicine (NEJM), the team said the vaccine showed significant protection against serotypes 1, 2, and 3 with efficacy levels of 73.1 percent, 97.7 percent, and 62.3 percent, respectively. They were not able to reach any conclusions for serotype 4 due to the low number of infections.

According to the MedicalXpress, the Takeda vaccine also reduced the risk of hospitalization by 95.4 percent among participants who had confirmed dengue infections. MedicalXpress is a web-based medical and health news service that features the most comprehensive coverage in the different fields of medicine.

It adds that the researchers regard the findings as encouraging, although they remain cautious.

"There may be an imbalance in the vaccine, particularly with dengue 3 and maybe dengue 4, but the efficacy was very good," said Anna Durbin, a dengue researcher at the Johns Hopkins Bloomberg School of Public Health who was not involved in the study.

The researchers will continue to monitor the participants, who will undergo testing for four and a half more years. If the drug is consistent with the results after that time, it will become eligible for widespread use.

Meeting Safety Standards

TAK-003 is the second vaccine against dengue that has been developed in the last few years. The first was Dengvaxia, developed by French pharmaceutical company Sanofi, which was pulled following serious concerns.

According to the Japan Times, Sanofi's vaccine demonstrated 59.2 percent overall efficacy in the first year of follow-up based on combined results of two late-stage trials. Dengvaxia became commercially available in 2016 in 11 countries; One of which is the Philippines, where the drug increased disease severity in some recipients of the 800,000 school-age vaccinated children.

The severity was found among children who had no prior dengue exposure when they were injected with Dengvaxia—prompting the Philippine government to investigate and halt the campaign for widespread use of the vaccine.

As the fallout increases the standard for demonstrating the safety of future dengue-fighting drugs, the Tekada trial shows better results than that of Sanofi. Still, there is still a need to remain cautious to avoid repeating the incident in the Philippines.

"We still need to wait for the full trial report to see if the efficacy persists and safety is assured," Leonila Dans, a pediatrician at the University of the Philippines in Manila, told peer-reviewed journal Science Magazine. "Ideally we want a vaccine that will be protective for all serotypes."


One of the effective vector control measures that should be done is applying insecticides to mosquito-infested areas during outbreaks. / Photo by: Bogdan Mircea Hoda via 123rf


A Desperately Needed Drug

After the incident with Sanofi, the need for another anti-dengue vaccine resurfaced—and the results of Takeda's trial came in just the right time. The promising results of the large trial imply that protection, albeit partial, against multiple dengue strains is possible.

People who develop antibodies to one dengue serotype are put at a higher risk of severe disease if they were infected by one of the other three strains. What's more, the antibody against the first serotype won't be able to stop the second virus and could actually speed up the infection process.

According to the WHO, dengue infections are also growing as travel, urbanization, and global warming continues—with about half of the world being at risk. In some Asian and Latin American countries, severe dengue was found to be the leading cause of serious illness and death among children and some adults.

There is no specific treatment for dengue or severe dengue yet and with the rise of the global incidence of the disease, the only way to swerve it off is to either prevent people from getting infected or detect infections early so it won't progress to a severe case. 

Aside from vaccines and early treatments, effective vector control measures should also be put into place. These measures include:

• Ensuring that the surroundings are clean and free of possible mosquito breeding sites.
• Minimizing skin exposure when going to mosquito-infested areas.
• Educating communities about the risks of mosquito-borne diseases.
• Applying insecticides to mosquito-infested areas during outbreaks.
• Active monitoring and surveillance of mosquito and virus infections.