Mr Johnson applauded the NHS from the doorstep of Number 10, while Labour leader Sir Keir Starmer applauded from his home in Kentish Town, north London, at 5pm on Sunday.
The Prince of Wales also paid tribute ahead of the event, which it is hoped will become an annual tradition.
Mr Johnson met NHS workers in the Number 10 garden on Sunday afternoon, while public buildings including the Royal Albert Hall, Blackpool Tower and the Shard have been lit up blue in tribute to the health service.
Speaking at a Downing Street press conference on Friday, the PM urged the public to clap for “those who have worked tirelessly and selflessly to help the nation get through this pandemic”.
Both Charles and Sir Keir paid tribute to the NHS in separate messages on Sunday.
The prince said: “The current pandemic means that the NHS – and the entire country – has been through the most testing time in the service’s history.
“Our remarkably selfless nurses, doctors, paramedics and countless other staff have made costly sacrifices to provide treatment for more than a hundred thousand patients with coronavirus and thousands more who needed other care.
“And, in tribute to them, we have come together as a nation to thank them for their skill, professionalism and dedication.”
Meanwhile, Sir Keir said the health service had a personal resonance for him as his late mother was a nurse and later relied on the NHS as she became ill.
He said: “Many, many times she got gravely ill and it was the NHS that she turned to, and I remember as a boy, a teenager, being in high dependency units, in intensive care units, with my mum, watching nurses and other support staff keep my mum alive.
“They did that on more than one occasion – it’s etched in my memory. For them, it was just the day job. They were doing that every day.
“So, it’s very personal for me and I’m very grateful to the NHS and my mum was very grateful, she loved the NHS through the many decades that she absolutely depended on them.”
On Saturday, people observed a minute’s silence and lit candles in remembrance of those who have died during the coronavirus pandemic.
The nationwide clap had been organised following a letter from the Together coalition, in which influential figures including NHS chief executive Sir Simon Stevens and the Archbishop of Canterbury Justin Welby voiced their support for making July 5 an official day of commemoration.
Sir Simon said he hoped the public will use the anniversary as an opportunity to “say a heartfelt thank you” to hospital staff.
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