CAMBRIDGE (CBS) – Moderna claims its’ coronavirus vaccine is showing promise in monkeys.

The Cambridge-based company said a new study found primates who were given the vaccine were able to fight off the virus.

The findings were published in the New England Journal of Medicine Tuesday.

This does not guarantee that the vaccine will work for humans but Moderna said in a statement it is “cautiously optimistic.”

The bio-tech company began phase three of its clinical trial Monday as it started testing the vaccine on 30,000 people.