Washington, Jan 12 : US President-elect Joe Biden has received the second dose of the Covid-19 vaccine, four weeks after he was administered the first shot. Biden was injected the second dose of the Pfizer-BioNTech vaccine on Monday at a hospital in Newark, Delaware, his home state where his transition headquarters are based, Xinhua news agency reported. He received the first dose on December 21, 2020. Wearing a short-sleeved polo shirt so that the jab can be easily injected into his arm, Biden urged Americans to continue wearing masks, waving a black one of his own. Taking to Twitter, he said: "Folks, I just received the second dose of my Covid-19 vaccine Â? and just like the first dose, it was safe, quick, and painless. "I urge everyone to get vaccinated once it's your turn. Because only together can we save lives and beat this virus. "Getting America vaccinated will be one of the greatest operational challenges we've ever faced, but my administration will spare no effort to get it done. "We're going to ensure the vaccine is distributed quickly, equitably, and free of charge to every American." The Pfizer vaccine, which, together with the Moderna vaccine, is being distributed across the country after gaining emergency use authorization -- requires two doses to be injected several weeks apart. So does the Moderna vaccine. Biden has recently vowed to release nearly all of the coronavirus vaccines the country now possesses after taking office on January 20, rather than withhold millions of vials to guarantee second doses are available. He also plans to get 100 million Americans vaccinated in his first 100 days in office. While the rollout of vaccines under the administration of outgoing President Donald Trump has been heavily criticised for being so slow that it failed to hit the initial target of delivering 20 million doses by the end of last year, Biden's plan seems to remain fluid, as reports surfaced that the President-elect vented frustration over the under-performance of his own transition team. Asked about his disappointment, Biden shrugged off those concerns by expressing confidence in his coronavirus task force. "I'm confident we can get done what we have to get done," said the President-elect, reiterating that some 3,000 to 4,000 Americans dying of the virus per day is "beyond the pale." Transition officials have complained about the lack of long-term planning by the Trump administration on immunizing the American people. The US distributed some 25.5 million vaccine doses as of Monday morning, and administered nearly 9 million first doses, according to data from the Centers for Disease Control and Prevention. The country still leads by a big margin in confirmed cases worldwide, now at 22,612,384, more than doubling the number in second-placed India, according to Johns Hopkins University. The death toll has increased to 376,051, also the highest in the world. /IANS