The United States on Friday authorized Moderna’s Covid-19 vaccine for emergency use, paving the way for millions of doses of a second jab to be shipped across the hardest-hit country in the world. The latest breakthrough came as many governments clamp down on socializing over Christmas and New Year, which is expected to fuel a jump in virus deaths in early 2021. Italy on Friday announced harsh new restrictions over the holidays with many shops and all bars and restaurants closed, travel between regions banned, and only one daily outside trip per household permitted. And parts of Sydney were heading into a fresh lockdown on Saturday, with Australian officials saying they hoped the restrictions would be enough to control a growing outbreak in time for Christmas. With the United States now registering over 2,500 deaths a day from Covid-19, senior US officials including Vice President Mike Pence stepped up to receive early vaccinations on Friday.