The Politico report said O'Brien was allowed to return to work at the White House after testing negative for COVID-19 two consecutive times and a week of showing no symptoms.
On 27 July, the White House said O'Brien tested positive for COVID-19 and exhibited mild symptoms. He contracted the disease during a vacation with his family.
O'Brien continued to work remotely from his home, which has a secure facility that allows him to access classified information, the report said.
As of 4 August, the US has registered nearly 4,650,000 COVID-19 cases and almost 154,500 fatalities related to the disease, the US Centres for Disease Control and Prevention data shows.