Fauci, 81, President Joe Biden’s chief medical adviser, tested positive on Wednesday.
The National Institutes of Health, which employs Fauci, said the doctor was experiencing mild symptoms.
Fauci has received not only a primary series of a COVID-19 vaccine, but two boosters, due to the waning effectiveness of the shots.
Opening the Senate Health Committee hearing, Chairwoman Patty Murray (D-Wash.), said that Fauci would be testifying remotely.
“Dr. Fauci, we do appreciate you joining us virtually, following your positive COVID test and of course we all do wish you a very speedy recovery,” she said.
“Tony, I hope you have a mild case,” added Sen. Richard Burr (R-N.C.), the top Republican on the panel.
Fauci, dressed in a suit and tie, did not address his own health during his opening statement or during early answers to questions.
He appeared to be tuning in from his home.
“Dr. Fauci will isolate and continue to work from his home,” the NIH said in its statement.
The agency said that Fauci would be following guidance from the Centers for Disease Control and Prevention, which recommends people who get COVID-19 isolate for five days, and medical advice from his physician.
Fauci does not plan on returning to the NIH until he tests negative.
Fauci tested positive on a rapid antigen test.
It wasn’t clear whether Fauci had been tested again with a polymerase chain reaction test, which is more reliable than an antigen test, or additional antigen tests.
A number of high-profile people have tested positive on an antigen test but soon tested negative once or multiple times, indicating a false positive.
During the hearing on Thursday, Fauci talked up vaccines, which have declined in effectiveness against both infection and severe illness as new variants of the CCP virus have emerged, including the Omicron variant.
“This variant has evolved with multiple mutations that are associated with an increased efficiency of transmission and immune evasion. Fortunately, our current vaccines have maintained their effectiveness in preventing severe COVID-19,” Fauci said.
“However, individuals who have received only their primary vaccine regimen have a greater likelihood of getting infected with the Omicron variant that with previous variants. And so importantly, booster shots have been shown to significantly reconstitute and enhance the level of antibodies that neutralize the Omicron variant and its sublineages.”
However, Fauci later acknowledged that there is “not enough data” to show a reduction in hospitalization or death for children who get a booster shot.
