Biden continues to 'improve steadily' after testing positive for COVID-19, his doctor says

President Joe Biden's symptoms from COVID-19 "continue to improve steadily," but he is "still experiencing a loose, non-productive cough and hoarseness," his doctor said on Saturday.

"His pulse, blood pressure, respiratory rate and temperature remain absolutely normal. His oxygen saturation continues to be excellent on room air. His lungs remain clear," Dr. Kevin O'Connor said in a new letter.

Biden completed his sixth dose of Paxlovid Saturday and results returned showing that the president's COVID variant is KP.2.3, which accounts for roughly a third of new cases in the U.S., according to the CDC.

O'Connor said Friday that Biden's symptoms had "improved meaningfully from yesterday."

Biden, 81, tested positive for COVID-19 on Wednesday, following a campaign event in Las Vegas, the White House said.

UnidosUS CEO Janet Murguía announced the diagnosis from the podium at a conference in Las Vegas where the president was set to speak.

"He is vaccinated and boosted and he is experiencing mild symptoms," the White House said in a statement Wednesday night. "He will be returning to Delaware where he will self-isolate and will continue to carry out all of his duties fully during that time."

In a statement Friday, Biden said he will be returning to the campaign trail next week.

First lady Jill Biden was in Rehoboth, Delaware, with the president as he self-isolated following his COVID diagnosis. Jill Biden was already in Rehoboth prior to the president's diagnosis, her office said on Thursday. No additional family is in Rehoboth, according to her office.

When asked if she has been tested for COVID or was showing any symptoms, her office said, "She is tested as determined appropriate by her doctor -- she is not symptomatic and up to date with her vaccines."

President Biden is being "kept up to speed" on national security matters while he isolates, national security communications adviser John Kirby told reporters Thursday afternoon.

"I think we can all understand that while he's certainly focused on getting better, as anybody who's had COVID would want to do, he is -- he's being kept up to speed as appropriate, by his leadership team, and certainly that includes on the national security front," Kirby said in an audio-only gaggle.

Kirby didn't have any specific briefings to speak to, but said that the president is being "kept updated and up to speed as he normally would."

The White House said it will provide regular updates on the president's status "as he continues to carry out the full duties of the office while in isolation."

The White House had shared a note Wednesday from Biden's doctor, who said the president had upper respiratory symptoms -- including a running nose and cough -- and "general malaise" Wednesday afternoon.

"He felt OK for his first event of the day, but given that he was not feeling better, point of care testing for COVID-19 was conducted, and the results were positive for the COVID-19 virus," his doctor said, according to the White House.

The president gave a thumbs-up to reporters as he prepared to depart Las Vegas on Wednesday when asked how he was feeling and responded, "Good. I feel good," according to the pool.

He was seen maskless boarding Air Force One in Las Vegas on Wednesday afternoon to head to Rehoboth.

Biden also shared his COVID-19 diagnosis on X later Wednesday night, writing, "I am feeling good and thank everyone for the well wishes."

"I will be isolating as I recover, and during this time I will continue to work to get the job done for the American people," he said.

Biden previously tested positive for COVID-19 in 2022 and took Paxlovid then, the White House said at the time.

The president was slated to deliver remarks Wednesday afternoon at the annual conference for UnidosUS, the nation's largest Hispanic civil rights and advocacy organization, when Murguía announced from the stage that he would no longer be able to appear.

"Regrettably, I was just on the phone with President Biden and he shared his deep disappointment at not being able to join us this afternoon," Murguía told the crowd. "The president has been at many events as we all know, and he just tested positive for COVID. So, of course, we understand that he needs to take the precautions that have been recommended, and he did not obviously want to put anybody at risk."

"He said to tell my folks that you're not going to get rid of him that quickly," Murguía continued. "We're going to have a chance to hear from him in the future directly. He's just really sorry he couldn't be with us."

ABC News' Mary K. Bruce, Molly Nagle and Justin Ryan Gomez contributed to this report.