Dr Anthony Fauci is back. In truth, America’s leading infectious-diseases expert never really went away. But after enduring nearly a year of darts and undermining comments from former president Donald Trump, Dr Fauci now speaks with the authority of the White House again. He said it was liberating to be backed by a science-friendly administration that has embraced his recommendations to battle Covid-19. “One of the new things in this administration is, If you don’t know the answer, don’t guess,” Dr Fauci said in one pointed observation at a White House briefing on Thursday. “Just say you don’t know the answer.” Dr Fauci’s highly visible schedule on Thursday, the first full day of President Joe Biden’s term, underscored the new administration's confidence in the doctor but also the urgency of the moment. His day began with a 4am online meeting with officials of the World Health Organisation, which is based in Switzerland, and stretched past a 4pm appearance at the lectern in the White House briefing room. The breakneck pace highlighted the urgent need to combat a pandemic that has killed more than 400,000 Americans and reached its deadliest phase just as the new president took office. _______________ _______________ Dr Fauci made clear that he believed the new administration would not trade in the mixed messages that so often came from the Trump White House, where scientific fact was often obscured by the president’s political agenda. "The idea that you can get up here and talk about what you know and what the science is ... it is something of a liberating feeling," Dr Fauci said after White House press secretary Jen Psaki invited him to take the podium. While choosing his words carefully, Dr Fauci acknowledged that it had been difficult at times to work for Mr Trump, who repeatedly played down the severity of the pandemic, refused to consistently promote mask-wearing and often touted unproven scientific remedies, including a malaria drug and even injecting disinfectant. “It was very clear that there were things that were said, be it regarding things like hydroxychloroquine and other things, that really was uncomfortable because they were not based in scientific fact,” Dr Fauci said. He said he took “no pleasure” in having to contradict the president, a move that often drew Mr Trump’s wrath. Mr Biden, during his presidential campaign, pledged to make Dr Fauci his chief medical adviser when he took office, and the 80-year-old scientist was immediately in action. He was up well before dawn on Thursday for the meeting with the WHO, which Mr Biden had rejoined the previous day after Mr Trump withdrew the US from the global body angered by the way it dealt with China in the early days of the pandemic. Dr Fauci told the WHO that the United States would join its effort to deliver coronavirus vaccines to poor countries. In the afternoon, the doctor stood alongside Mr Biden and Vice President Kamala Harris in the White House as they unveiled a series of executive orders aimed at slowing the spread of the virus, which is killing more than 4,000 Americans a day, as well as bolstering the nation’s sluggish vaccine distribution programme. It was all a stark contrast after being kept on a tight leash by the Trump administration, which had tightly controlled Dr Fauci’s media appearances and blocked most of them. The doctor went from being a constant presence in the briefing room during the first weeks of the pandemic to largely being banished as Mr Trump grew jealous of his positive press and resentful of Dr Fauci's willingness to contradict him. Moreover, Mr Trump frequently undermined Dr Fauci’s credibility, falsely insisting that the pandemic was nearly over. The president regularly referenced Dr Fauci's early scepticism about the effectiveness of masks for ordinary Americans, a position that the doctor quickly abandoned in the face of more evidence. The president's attacks on Dr Fauci – and his dismissiveness of the science – handicapped medical professionals trying to get Americans to take the virus seriously. “There was clear political influence on the message of the pandemic. It became political to say that the pandemic was devastating our community because it was interpreted as a judgment on Trump,” said Nahid Bhadelia, an infectious-diseases physician and a professor at the Boston University School of Medicine. “It actively created enemies of the public health folks in a segment of the population.” Having Dr Fauci return to a central role, Dr Bhadelia said, is a sign “that science was being repressed and [is] now back”. As his handling of the pandemic became the defining issue in the 2020 campaign, Mr Trump insisted on portraying the virus as a thing of the past. He also mercilessly attacked Dr Fauci, retweeting messages that called for the doctor’s dismissal and revelling in “Fire Fauc!” chants at some of his rallies. Mr Trump sidelined the expert but dared not dismiss him, after aides convinced him of the move’s political danger. But Dr Fauci, who has now served under seven presidents, persevered, telling friends that he would keep his head down and aim to outlast Mr Trump and the obfuscations of his administration. “Clarity of message is the most important thing the government can be doing right now; the single biggest disservice Trump did was constantly telling people the pandemic was about to be over,” said Ashish Jha, dean of the Brown University School of Public Health, who has known Dr Fauci for more than 20 years.