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.

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

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

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