Jimmy Fallon Savagely Mocks President Biden Over Covid Diagnosis

Jimmy Fallon crapped on President Joe Biden in his opening monologue -- cracking jokes about the Prez's COVID news ... and questioning if Round 2 in the Oval Office is in store.

The 'Tonight Show' host made some jokes at JB's expense on Thursday's episode -- saying POTUS was lucky he couldn't spread his diagnosis ... especially since Democrats had already been distancing themselves from him after that debate debacle with Trump.

JF didn't stop there ... adding, "Thankfully, Biden is expected to make a full recovery, and his doctor said that he'll be back to 60% in no time." Obviously, he's referring to questions about Joe's cognitive abilities for a second term.

He also had a laugh about who might've given Biden COVID ... playfully pointing fingers at Kamala Harris. And to top it off, he joked the diagnosis was the first "positive" news Joe has heard in ages. Funny stuff, no doubt ... but it's telling that Jimmy's piling in a primetime slot.

Jokes aside, it looks like Biden will be just fine. His press secretary, Karine Jean-Pierre, said he’s fully vaccinated and boosted, and was only experiencing mild upper respiratory symptoms -- just enough to make him want to get tested.