In a video on Twitter, the Conservative Party leader said he had witnessed the “personal courage” of hospital staff on the front line.
He said NHS workers “kept putting themselves in harm’s way, kept risking this deadly virus”.
“It is thanks to that courage, that devotion, that duty and that love that our NHS has been unbeatable,” he went on.
It comes as Jeremy revealed he was isolating with his girlfriend Lisa Hogan and her daughter at his farm.