The EU's drug agency on Monday approved the storage of the Pfizer-BioNTech coronavirus vaccine in fridges for up to a month, in a move that should boost its rollout across the bloc.

The storage period in fridges of unopened vials of the vaccine, which initially had to be stored in super-cooled freezers, had been lengthened from five days, the European Medicines Agency said.

"Increased flexibility in the storage and handling of the vaccine is expected to have a significant impact on planning and logistics of vaccine rollout in EU member states," the Amsterdam-based EMA said.

"This change extends the approved storage period of the unopened thawed vial at two-eight degrees Celsius (35 to 46 Fahrenheit) [i.e. in a normal fridge after taking out of deep-freeze conditions] from five days to one month (31 days)," it added.

The Pfizer vaccine's high effectiveness against coronavirus has been tempered by the difficulty of storing and transporting the jab due to the need for the super-cold conditions originally required.

In March the EMA said however that the jab could be stored in normal freezers, before allowing it to remain for fridges for short periods of time.

German developer BioNTech, which makes the vaccine along with US pharma giant Pfizer, said the EMA had made the decision based on new information it had supplied.

"The change of the storage conditions is based on new data from stability studies that confirmed the product quality for 31 days," it said in a statement.