Dengue vaccine meets main goal of trial

CHICAGO: Takeda Pharmaceutical said on Tuesday that its experimental dengue vaccine appears to be safe and effective at preventing all four types of the mosquito-borne disease, meeting the main goal of the Japanese drugmaker’s late-stage clinical trial.

The company said no significant safety concerns have emerged to date with vaccine called TAK-003.

Takeda did not disclose how the vaccine performed in people who had never been previously exposed to dengue, a group that experienced an increased risk of severe disease with Sanofi’s Dengvaxia, the world’s first dengue vaccine.

Sanofi had not collected blood samples on all subjects prior to beginning its trials. By the time the company confirmed the safety risk in 2017, the vaccine had already been used in more than 800,000 school children in the Philippines.

Takeda collected blood samples from all 20,000 children aged 4 to 16 from Asia and Latin America who participated in the Phase III TIDES trial. The study looked at the vaccine’s safety and efficacy both in children who had been exposed to dengue and those who had not.

Takeda said it will release full details of how the vaccine fared at 15 months after the first dose in a peer-reviewed journal as quickly as possible.

The vaccine is administered in two doses three months apart. The first efficacy results include 11 months of follow-up.

Part 2 of the trial, which includes another six months of patient data, will review how the vaccine performed in each of the four different types of dengue, as well as its performance according to prior dengue exposure and the number of participants who contracted severe dengue.

Those two parts will form the basis of Takeda’s filings seeking regulatory approvals. A third part of the study will evaluate long-term safety by following participants for another three years.

Dr. Rajeev Venkayya, president of Takeda’s vaccines business, said in a phone interview that the upcoming publication will include preliminary data on the vaccine’s performance against each dengue strain and data on prior dengue exposure of trial subjects.

The first safety problems with Sanofi’s vaccine only became apparent in the third year after vaccination. After the Sanofi experience, some experts believe governments will require several years of follow-up data before incorporating Takeda’s vaccine into mass vaccination campaigns.

Venkayya would not speculate on how much follow-up regulators or health authorities will require, but said, “I do think it’s going to be more than one year.”

While Sanofi’s vaccine was based on a Yellow fever virus with dengue genes added in, TAK-003 is based on a weakened dengue 2 virus plus genes from the three other dengue types. Some infectious disease experts think the all-dengue design may trigger a broader immune response.