"Biden... tested positive again while testing for antibodies to COVID-19 on Wednesday," RIA Novosti reported.
There are no new symptoms in the wife of the American president.
US President Joe Biden tested negative on Wednesday.
On August 16, Jill Biden tested positive for coronavirus.
For the first time, US President Joe Biden passed a positive test for coronavirus infection on July 21, while on July 27 the test showed a negative result, and the head of the United States announced a return to full-time work after suffering COVID-19.
A few days later, he again passed a positive test for coronavirus.
On August 7, the second test of the American leader for coronavirus showed a negative result.