Story highlights Although malaria deaths have declined, 429,000 died in 2015

The RTS,S malaria vaccine, known as Mosquirix, is the furthest along

(CNN) The World Health Organization announced Monday that it has the go-ahead to try the first malaria vaccine in the field in real-world settings next year. The organization made the announcement on the eve of World Malaria Day.

More than 429,000 people lost their lives to the mosquito-borne illness in 2015, and hundreds of millions get sick with a malaria infection every year. Some never fully recover.

There has been enormous progress in fighting the disease. From 2000 to 2015, there was a 62% reduction in malaria deaths, according to the WHO, and a 41% reduction in the number of cases . There have been fewer deaths in large part because of better mosquito control and disease awareness, as well as sustained effort to get the right medicine to the right populations, experts said.

But there are gaps in prevention coverage, particularly in regions such as sub-Saharan Africa, where about 43% of people at risk for the disease don't have access to mosquito protection like bed nets or bug spray, according to the WHO.

Africa is the continent that sees the highest number of malaria cases. The new vaccine will be tested in Kenya, Ghana and Malawi starting in 2018.