The White House has identified 17 individuals, including senior staff members and members of Congress, as "close contacts" to U.S. President Joe Biden who tested positive for COVID-19 on Thursday, White House Press Secretary Karine Jean-Pierre said at a press briefing on Friday.

Vice President Kamala Harris was identified as a close contact, but said she had tested negative for COVID-19. None of the staff members considered close contacts have tested positive to date, according to Jean-Pierre.

A person determined as a close contact must be less than six feet away from someone with confirmed or suspected COVID-19 for a cumulative total of 15 minutes or more over a 24-hour period, according to the Centers for Disease Control and Prevention.

Biden's symptoms have improved, with pulse, blood pressure, respiratory rate and oxygen saturation remaining normal. Fully vaccinated and twice-boosted, Biden is anticipated to respond favorably, according to the White House.

Biden is the second U.S. president to get COVID-19. His predecessor, Donald Trump, was struck by the virus in October 2020, when vaccines weren't available and treatment options were limited.