"This is another encouraging step forward, although I stress that this is preliminary, the safety data is limited and their production facilities are not yet at scale," Hancock said.
Interim data from a late-stage trial indicated Moderna's vaccine was 94.5% effective in preventing COVID-19.
Britain had previously secured supply deals for a total of 350 million vaccine doses from six different suppliers, including Pfizer Inc, whose vaccine was found to be more than 90% effective, and 100 million doses of an AstraZeneca/Oxford candidate expected to report late-stage results in coming weeks.
Asked if he regretted not being able to buy more of the Moderna vaccine, Hancock said Britain expected to have other vaccines sooner.
Britain expects to take delivery of the Pfizer vaccine before the Moderna shot becomes available, as well as AstraZeneca's candidate if it proves to be effective.