Delta COVID-19 Variant Could Evade Vaccine, 'Worst' Strain Yet By Danielle Ong Taiwan has struggled to secure enough vaccine doses for its 23 million people White House infectious disease expert Dr. Anthony Fauci has urged Americans to get vaccinated against COVID-19 to prevent the new variant, known as Delta or B.1.617, from spreading across the United States. Some Experts have labeled the variant the “worst we’ve seen so far.” During a Tuesday briefing of the administration’s pandemic response team, Fauci, the director of the National Institute of Allergy and Infectious Diseases (NIAID), warned that the recent coronavirus outbreak in the United Kingdom, which imperiled its plans to fully reopen on June 21, could happen in the United States.