https://www.scientificamerican.com/article/covid-vaccine-excitement-builds-as-moderna-reports-positive-result/ > They say good news comes in threes. For the third time in a week, a coronavirus vaccine developer has reported preliminary results suggesting its vaccine is highly effective. > Today, biotech company Moderna in Cambridge, Massachusetts, reported that its RNA-based vaccine was more than 94% effective at preventing COVID-19, based on an analysis of 95 cases in its ongoing phase III efficacy trial.