Senator Rand Paul said he was surprised that Anthony Fauci invoked the Fifth Amendment during a Senate hearing on the COVID-19 pandemic, arguing that a pre-emptive pardon from former President Joe Biden should have removed the risk of self-incrimination. The dispute matters because it intensified a long-running political and scientific clash over Fauci’s pandemic-era role, federal research funding and the origins of COVID-19.

Fauci declined to answer questions at the Republican-led hearing on the advice of his lawyers, saying Paul’s calls for his prosecution had left him concerned about the proceedings. Paul has accused Fauci of misleading Congress about US-funded research connected to Wuhan, an allegation Fauci and federal health officials have disputed; Paul said he would pursue contempt proceedings.