WASHINGTON, July 29 -- Dr. Anthony Fauci sat at the witness table in Senate Room 342 on Wednesday and said almost nothing.

After 38 years directing the National Institute of Allergy and Infectious Diseases and more than 200 congressional appearances, the 86-year-old infectious disease expert declined to answer a single question at a Senate hearing on COVID-19's origins. He invoked his Fifth Amendment right against self-incrimination for the first time in his career. "It pains me to do so," he said in an opening statement, "because of the respect that I have for the legislative branch."

The hearing, convened by the Senate Homeland Security and Governmental Affairs Committee under its chairman, Senator Rand Paul of Kentucky, was designed ...