March 19 (UPI) -- Dr. Anthony Fauci, chief adviser to President Joe Biden and the nation's top infectious diseases expert, clashed with a Senate Republican on Thursday over a precautionary measure intended to stem the spread of COVID-19.Fauci and Centers for Disease Control and Prevention Director Rochelle Walensky, both of whom are members of Biden's COVID-19 Response Team, appeared before the Senate health, education, labor and pensions committee to answer questions about the ongoing federal response. During the hearing, Fauci was pressed by Sen. Rand Paul, R-Ky., about the effectiveness of masks in mitigating transmission rates. In his remarks, Paul suggested that wearing masks is only "theater" after getting the vaccine -- and directly criticized Fauci for wearing two masks during the hearing, which health experts say is even more effective in reducing transmission of the virus.RELATED Stephen Colbert to mark a year in quarantine with special 'Late Show' Friday"You're telling everyone to wear a mask," Paul said. "If we're not spreading the infection, isn't it just theater? You have the vaccine and you're wearing two masks, isn't that theater?" "Here we go again," Fauci, who has already received both doses of Moderna's vaccine, answered. "[I will] state for the record that masks are not theater" he added. "I totally disagree with you."