British Prime Minister Boris Johnson has said it is too early to say if England's lockdown can end on June 21 as data on whether the vaccine rollout offers enough protection from the rapid spread of the Delta coronavirus variant is still being assessed.

“On Monday ... we'll have a look at where we are. I think what everybody can see very clearly is that cases are going up, and in some cases hospitalisations are going up,” Johnson said.

“What we need to assess is the extent to which the vaccine rollout, which has been phenomenal, has built up protection in the population in order for us to go ahead to the next stage. And so that's what we'll be looking at.”