Happy anniversary, India.

Six years ago today, you became polio-free, bringing the world that much closer to eradicating the crippling childhood disease altogether.

India was once considered the most challenging country in the world for eradicating polio because of its incredible density: it has a population of more than 1 billion and critical sanitation issues.

Read More: Polio: Why It Hasn’t Been Fully Eradicated — Yet

Thirty years ago, before the Global Polio Eradication Initiative began its effort to rout out polio around the world, 200,000 Indian children were diagnosed with polio every year. And just a few years ago, in 2009, India was responsible for over half of all polio cases in the world.  The challenge was enormous.

The first polio immunization campaign took place in 1995. Since then, more than 2 million volunteers have swept across the country immunizing India’s next generation, providing some 12 billion doses of the polio vaccine to Indian children.

Read More: Nigeria Polio Outbreak: Global Citizen Calls on World Leaders to Act

In 2011, India had its last case of polio.

Ending polio in India was no easy task; it took a joint effort between government and civil society groups like WHO, UNICEF, Rotary International, the US Centers for Disease Control and Prevention, The CORE Group Polio Project, the Bill and Melinda Gates Foundation, and the US and Japanese government aid agencies.

Take Action: We’re 0.1% Away from Eradicating Polio for Good

Today, newborns in India receive routine vaccines, a critical step to helping rout out the disease from the population and prevent its reemergence. And now India serves as a model for the three countries where polio remains: Pakistan, Afghanistan, and Nigeria.

So congratulations, India, and polio, take note: we’re coming for you in Afghanistan, Nigeria, and Pakistan in 2017.