LONDON (AP) — Results from an early test of a dengue vaccine suggest it isn’t ideal, but scientists say the study is still encouraging news in the global fight against the disease known as “break-bone fever.”

There is currently no treatment or vaccine for dengue, which causes symptoms including fever, severe joint pain, headache and bleeding. The mosquito-borne disease infects up to 100 million people worldwide every year, mostly in Asia, Africa and Latin America.