Britain had previously secured supply deals for a total of 350 million vaccine doses from six different suppliers, including Pfizer Inc.
Britain has secured 5 million doses of an experimental 
COVID-19 
vaccine developed by Moderna Inc after it reported positive trial results, health minister Matt Hancock said on Monday, with the earliest doses expected for delivery in spring.
Interim data from a late-stage trial indicated Moderna's 
vaccine was 94.5% effective in preventing 
COVID-19.
"We have today secured an initial agreement for 5 million doses of the Moderna 
vaccine," Hancock said at a news conference.
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.
Earlier, Prime Minister 
Boris Johnson's spokesman said the government had prioritised deals with 
vaccine developers who could provide early supply to Britain and have advanced manufacturing supply chains in place.
Asked if he regretted not being able to buy more of the Moderna 
vaccine, Hancock said Britain expected to have other 
vaccines sooner.
"The Moderna 
vaccine doesn't come on stream until the spring," Hancock said.
"I'm just really pleased that we've got those early 
vaccines that will be available early, and we've already got the orders of those in."
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.
Deputy Chief Medical Officer Jonathan Van Tam said data from late-stage trials of the 
AstraZeneca/Oxford 
vaccine had not been reviewed, so it was still unknown if it works.
But he added that trial results from both the 
Pfizer and partner 
BioNTech vaccine and Moderna's augured well for other candidates that target the 
coronavirus' spike protein.
"This really does begin to show us that the spike protein is a completely plausible and effective target for 
vaccines to be working against," Van Tam said.
"We're feeling in a happier place than we were. But do we know the (Oxford/
AstraZeneca) data? No we don't."