Dr. Anthony Fauci warned Tuesday that the dangerous Indian COVID-19 variant could become the most dominant strain in the US — as the mutation has rapidly spread among younger people in the UK. The White House chief medical adviser said he feared that the so-called Delta variant, B1.617.2, could overtake the highly contagious UK variant, known as B117, in the country — an alarming prospect we should prevent. “We cannot let that happen in the United States, which is such a powerful argument … to get vaccinated,” Fauci said Tuesday at the White House COVID-19 task force briefing.