One batch of Oxford coronavirus vaccine meant for Wales has failed testing
One of the four batches of the Oxford vaccine Wales was due to receive this week has failed testing, according to First Minister Mark Drakeford.
Mr Drakeford has been forced to defend the speed of the vaccination programme in Wales.
"One of those batches has not come through the testing process and we will get it next week we're told instead," Mr Drakeford told Sky News.
"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."
Mr Drakeford said around 150,000 people would have been vaccinated in Wales by the end of Monday.
"We're getting more supplies of vaccine this week, particularly the Oxford vaccine and we'll be able to use all of that," Mr Drakeford said.
"We're on track to vaccinate the top four priority groups by the middle of February, alongside the other UK nations.
"There's a long way to go with vaccination. We're going to be doing this for months and months, not just for weeks.
"So it's very important to get all the infrastructure in place. We've expanded the number of mass vaccination centres."
Of the four nations of the UK, Wales is lagging behind in delivering the first dose of the vaccine per 100,000.
As of last week 3,215 had received it in Wales, compared with 3,514 in Scotland, 4,005 in England and 4,828 in Northern Ireland.
"These are very marginal differences and I don't think these are the most important issue," Mr Drakeford said.