More than a million people have received their first dose of a Covid-19 vaccine in the United States, authorities said on Wednesday. Centers for Disease Control and Prevention called it an early but important milestone. The US is aiming for 100 million people immunized by the end of the first quarter of 2021, and another 100 million by the second quarter. The US is the world's hardest-hit country and more than 3,20,000 people have succumbed to the virus so far. The authorities have shipped 15.5 million doses of coronavirus vaccines across the United States with up to five million more slated for delivery before year-end