LONDON: Britain said it was in advanced talks to access an experimental COVID-19 vaccine developed by Moderna Inc after it reported positive trial results on Monday, adding it would be available in Britain from in spring 2021 at the earliest.

Interim data from a late-stage trial indicated Moderna's vaccine was 94.5% effective in preventing COVID-19.

Although Britain has secured a total of 350 million doses of vaccine candidates from six different suppliers - including a Pfizer Inc. vaccine found to be more than 90% effective - it does not have a finalised agreement for the Moderna vaccine.

"As part of the ongoing work of the Vaccines Taskforce, the government is in advanced discussions with Moderna to ensure UK access to their vaccine as part of the wider UK portfolio," a government spokesperson said.

"Moderna are currently scaling up their European supply chain which means these doses would become available in spring 2021 in the UK at the earliest."

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.