Less than seven months after kicking off its largest vaccine trial to date, Takeda has finished enrolling 20,100 children for a mammoth phase 3 dengue study in eight endemic countries.

Investigators are conducting the study—which will test two doses of TAK-003 versus placebo three months apart—in Latin American and Asian countries in children aged 4 to 16. They’re looking to see whether Takeda’s vaccine can protect against dengue of any severity from any serotype regardless of previous exposure to the virus.

The enrollment "reflects Takeda’s prioritization of dengue and the substantial capabilities of our global organization," Takeda’s vaccines president Rajeev Venkayya said in a statement.

Takeda kicked off the study back in September, with execs pointing out that the drugmaker’s vaccines unit had to undergo a growth spurt just to get to that point. Part of that expansion meant committing €100 million ($107 million) to build a manufacturing plant for the shot in Singen, Germany.

If approved, Takeda’s vaccine would take on Sanofi’s first-to-market Dengvaxia, which has fallen short of the French drugmaker’s initial sales expectations despite the fact that it took 20 years and $1.5 billion to develop.

Analysts have predicted Takeda’s vaccine could steal market share by 2020, with some industry-watchers predicting dengue vaccines will reach $1 billion or more in yearly sales.

Dengvaxia has notched marketing approvals in 14 countries, but it is seen as an imperfect immunization against a virus that causes 390 million infections and 20,000 deaths each year.

Pushing on a global growth path in vaccines, Takeda is also working with the U.S. government on a Zika program and with the Bill & Melinda Gates Foundation to eradicate polio.

TAK-003 has already been through numerous earlier studies that have demonstrated its safety and immunogenicity against dengue’s four serotypes.