The Prime Minister has praised the "outstanding performance" of a Cwmbran vaccination centre as his visit to Wales was criticised for being deemed "non-essential".
Speaking from a mass vaccination centre at Cwmbran Stadium Mr Johnson said, "I think that across the whole of the UK there has been an outstanding vaccination performance.
"I think it's 46,000 they've done in this centre, a really outstanding achievement.
"I think, as the song goes, 'I've been all around the world and then Japan, I've never found a place for vaccines like Cwmbran'. How about that?"
Boris Johnson used the rap song 'Fresh Prince of Cwmbran', by Newport-born comedy hip hop group Goldie Lookin' Chain, to commend the work of vaccinators there.
On Wednesday, Public Health Wales figures showed a total of 807,351 people had received their first dose of the vaccine which is almost one in three in Wales.
Boris Johnson said the UK Government would continue to have conversations with devolved administrations about how best to exit lockdown.
"We had continuous conversations with Mark Drakeford, with other representatives of the devolved administrations, about how to do it, just as we work on the vaccination programme together," he said.
"I'm trying to make sure that we concert our approach and concert our general messaging."
But last year Mr Drakeford called on Mr Johnson to better engage with the devolved nations during a spike in infections.
The visit comes after a trip to Scotland in January, when questions were raised as to whether this could be classed as essential travel, including by First Minister Nicola Sturgeon.
On Wednesday, Wales' minister for mental health questioned how essential his latest visit was.
Eluned Morgan said, "We have a 'stay at home' message and you should not be travelling unless it's essential. I'm not sure if Boris Johnson's visit comes under the essential category."
In response to the visit, Plaid Cymru’s Westminster leader, Liz Saville Roberts MP described it as a "pointless 140-mile cross-border journey".
“This was a pointless 140-mile cross-border journey to Wales to make public comment on matters relating to England only", she said.
"He must urgently explain why he saw it appropriate to set about deliberately creating confusion about lockdown measures at a crucial stage in the pandemic.
“After a year of consistently overpromising and underdelivering, the people of Wales deserve better than to be misinformed by his blustery publicity machine.”
Leader of the Welsh Conservatives Andrew RT Davies tweeted to say the prime minister is "more than welcome and entitled to visit Wales."
"The Prime Minister serves & works on behalf of the entire United Kingdom, and is more than welcome & entitled to visit Wales & pay thanks to those on the frontline. "No story here, particularly when Labour members are moving around across the country", he added.
Mr Johnson said he would be providing more information on Covid rates and the vaccination rollout on Monday.
"I think that overall, if you look at infection rates across the UK, they are coming down a bit now, that's very encouraging.
"I think the big question people will want to ask is, 'to what extent now is that being driven by vaccination?' and we hope it is, there are some encouraging signs, but it's still early days."
During the visit, Mr Johnson said he felt "like OJ Simpson" as he struggled to pull on a pair of gloves.
The Prime Minister made the reference to the moment in Simpson's murder trial when the US actor and sports star had difficulty putting on gloves thought to have been used in the killing of his ex-wife, Nicole Brown Simpson, and her friend, Ronald Goldman.
The Prime Minister also visited the South Wales Police Headquarters in Bridgend, where he spoke to officers and heard about how they have been dealing with the pandemic.
Boris Johnson was heard telling officers: "Thank you for very much for all you've been doing. It's been a long, long haul but we're going to get through it and I think we're coming towards the final few furlongs now, I would say. Thank you very much indeed.
He continued: "I think it was very confusing as first [for the public], it was terribly difficult to get people to see the balance of what they needed to do."
In November, Mr Johnson allegedly described devolution as "a disaster north of the border" and that it had been "Tony Blair's biggest mistake".
Asked whether he still felt it was a disaster, he said: "Certainly not overall. I speak as the proud beneficiary of devolution.
"When I was running London I was very proud to be doing things that made a real difference for my constituents and electorate, improving quality of life, making sure that we drove down crime and did everything we could to give advantages to young kids.
"Devolution can work very well, but it depends very much on what the devolved authorities do."