A shot every one to three months may someday give an alternative to the daily pills that some people take now to cut their risk of getting HIV from sex with an infected partner.

Scientists say a long-acting, experimental drug completely protected monkeys from infection in two studies reported at an AIDS conference in Boston on Tuesday.

If testing in people shows the same, the shots could become a new tool to curb the spread of HIV. There’s already a daily pill that can be taken by those who don’t have the virus but are at risk of getting it from an infected partner.

The studies were done by the Centers for Disease Control and Prevention and researchers at Rockefeller University in New York.