Video above: California doctors and nurses receive 2nd vaccinationWhile hopes of vaccinating 20 million people by New Year’s Day sputtered out, the U.S. now faces staggering new challenges in the fight against COVID-19.About 15.4 million vaccine doses have been distributed in the U.S., but only 4.5 million people have received their first doses, the U.S. Centers for Disease Control and Prevention said Monday.That’s far behind