The analysis was based on the first 95 to develop Covid-19 symptoms.
Only five of the Covid cases were in people given the vaccine, 90 were in those given the dummy treatment. The company says the vaccine is protecting 94.5% of people.
The data also shows there were 11 cases of severe Covid in the trial, but none happened in people who were immunised.
"The overall effectiveness has been remarkable... it's a great day," Tal Zaks, the chief medical officer at Moderna, said.
"This is a pivotal moment in the development of our Covid-19 vaccine candidate. Since early January, we have chased this virus with the intent to protect as many people around the world as possible. All along, we have known that each day matters,”Stéphane Bancel, chief executive officer of Moderna, said.
"This positive interim analysis from our Phase 3 study has given us the first clinical validation that our vaccine can prevent Covid-19 disease, including severe disease," Bancel added.
The company warns that as new data becomes available, the assessment of the effectiveness of the vaccine may change. However, the company will apply for an Emergency Use Authorisation (EUA) with the US Food and Drug Administration (FDA) and will submit applications to global regulatory agencies.
That US process authorisation process could take two months. Moderna said it was on track to develop 500 million to 1 billion doses globally in 2021.
As we reported earlier, a front-runner coronavirus vaccine developed by drug giant Pfizer and German biotechnology firm BioNTech has shown 90% efficiency in the interim results of the third phase of clinical trials.
Their vaccine has been tested on 43,500 people in six countries and no safety concerns have been raised.