Wales First Minister Mark Drakeford told Sky News one of the four batches of the Oxford vaccine his country was due to receive this week had failed testing.
“One of those batches has not come through the testing process and we will get it next week we’re told instead,” Mr Drakeford said.
“Everybody is working absolutely flat out from the manufacturers through to the people who do the vaccination at the practical end.
“When you’re trying to do everything on a massive scale and at such speed there are going to be moments where not everything goes according to plan.
“But we are assured we will get that supply in exchange for this week next week, and we will be able to use it all then.”
It comes as there are also delays with the Pfizer jab.
Vaccines minister Nadhim Zahawi said an upgrade to the Pfizer manufacturing process could cause some delays.
He told BBC Radio 4’s Today programme: “There’s bound to be delays because any new manufacturing process has challenges at the outset. It is lumpy, it begins to stabilise and get better and better week in, week out.
“It could delay supply but I’m confident we can meet our target by mid-February of the top four cohorts.”
