Johnson, who tested positive for the coronavirus on March 26, was taken to St Thomas' hospital, in London, on Sunday.
He was treated in intensive care for three days before returning to a ward on Thursday.
In a video message, Johnson thanked all health staff who put their lives at risk in order to save the lives of others.
The United Kingdom has so far reported 84,279 confirmed coronavirus cases, with more than 10,000 deaths. (ILKHA)