The Americas are now free of measles and we have vaccines to thank, the Pan American Health Organization said earlier this week.

This is the first region in the world to be declared measles-free, despite longtime efforts to eliminate the disease entirely. The condition — which causes flu-like symptoms and a blotchy rash — is one of the world’s most infectious diseases. It’s transmitted by airborne particles or direct contact with someone who has the disease and is highly contagious, especially among small children.

To be clear, there are still people with measles in the Americas, but the only cases develop from strains picked up overseas. Still, the numbers are going down: in the US this year, there have been 54 cases, down from 667 two years ago. The last case of measles that developed in the Americas was in 2002. (It took such a long time to declare the region measles-free because of various bureaucratic issues.)

Health officials say that credit for this victory goes to efforts to vaccinate against the disease. Though the measles, mumps, and rubella (MMR) vaccine is recommended for all children and required by many states, anti-vaxxers have protested it due to since-discredited claims that vaccines can cause autism.

To stop transmission, 90 to 95 percent of people in a given region need to be vaccinated according to Seth Berkley, who runs the nonprofit GAVI, which promotes vaccination and immunization. In the US, that number is around 90 percent, but worldwide the number is only about 80 percent. Though declaring the Americas free of measles is a big step, people should keep vaccinating to ensure the disease doesn’t come back, experts say.