The results come five days after Biden spent more than 90 minutes with US President Donald Trump, who was diagnosed with covid-19 days after the debate that brought the two candidates face to face.
Joe Biden had already had two negative fronts on Friday.
The Democratic candidate plans to visit Florida on Monday and his campaign has said he will continue to observe public health guidelines on masks, social distancing and crowd size.
On Sunday, the President of the United States, Donald Trump, hospitalized since Friday, briefly left the hospital in a caravan of vehicles to welcome supporters abroad, after returning soon to the Walter Reed Military Medical Center.
Trump left the hospital in an armored SUV and remained in the vehicle, wearing a mask, as he passed a crowd that waved flags and applauded.
During Sunday’s briefing on the state of health of the head of state, White House doctor Sean Conley admitted the possibility of Donald Trump leaving hospital on Monday.
The doctor added that the president’s health “continues to improve,” but revealed that Donald Trump was treated with steroids after two drops in his oxygen levels on Saturday.
Trump is 74 years old and clinically obese, putting him at increased risk of serious complications from the virus that has infected more than 7 million people and killed more than 200,000 people in the United States.
On Friday, Donald Trump announced on his personal page on the social network Twitter that, like the first lady, Melania, had tested positive for the coronavirus and would be quarantined.
A few hours later, he was admitted as a precaution to the Walter Reed Military Hospital.