US President Joe Biden, who tested positive for COVID on Thursday, is getting better and is tolerating his treatment well, his personal physician said in a letter released by the White House on Saturday.

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"His symptoms continue to improve," wrote Dr. Kevin O'Connor, who had already claimed the day before that the president was better.

Mr Biden, 79, still suffers from a sore throat, cough, muscle aches and a runny nose.

The Democrat, who received a full COVID-19 vaccination, is being treated with paxlovid, an anti-COVID pill from Pfizer.

He "continues to tolerate the treatment well," said his doctor.

This antiviral drug works by decreasing the ability of the virus to replicate, thus stopping the progression of the disease.

It is recommended in the United States for people at risk of developing a severe case of the disease, a category into which the American president falls due to his age.

The president was likely infected with Omicron's BA.5 subvariant, added Kevin O'Connor.

Highly contagious, this variant is dominant in the country, where it accounts for approximately 80% of cases.