Rochelle Walensky, director of the Centers for Disease Control and Prevention (CDC), has tested positive for COVID-19 again after completing a round of the coronavirus antiviral treatment Paxlovid. Walensky tested positive for COVID-19 earlier this month, going into isolation and taking “appropriate action” for her health.

On Monday, the CDC said Walensky had experienced “mild symptoms” during her infection and eventually tested negative for the virus after completing a round of Paxlovid. “On Sunday, Dr. Walensky began to develop mild symptoms and has again tested positive. Consistent with CDC guidelines, she is isolating at home and will participate in her planned meetings virtually,” the agency said.

This apparent case of Paxlovid rebound is not surprising. White House chief medical adviser Anthony Fauci and President Biden both tested positive for COVID-19 again following a round of Paxlovid. A similar phenomenon has been observed in the Merck and Ridgeback coronavirus antiviral molnupiravir. COVID-19 rebound can also occur when antivirals are not administered.

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