Pfizer workers are gearing up for a mass rollout of the company's Covid-19 vaccine. The United Kingdom became the first country to approve Pfizer's vaccine. "I'm just so, so pleased that, you know, 2020 has been just awful and 2021 is going to be better. And help is on its way," said Matt Hancock, the U.K.'s Health Secretary. Pfizer's vaccine has yet to receive emergency use approval in the United States, but officials anticipate vaccinating 100 million Americans by the end of February 2021. For access to live and exclusive video from CNBC subscribe to CNBC PRO: https://cnb.cx/2NGeIvi The U.K. this week became the first country to authorize Pfizer’s coronavirus vaccine for emergency use, likely adding pressure on the U.S. Food and Drug Administration to quickly do the same. To be sure, the U.S. and the U.K. review vaccines differently. Pfizer had been submitting data on its vaccine with BioNtech on a “rolling basis” to the U.K., meaning regulators there were able to review the data in real time and do so until there was enough evidence to support a formal authorization. A rolling review is a tool that regulators use to speed up the assessment of promising drugs or vaccines. In the U.S., the FDA will go through every aspect of the data submitted in the application, including reviewing all safety information “to make sure there are no cracks” and everything is “solid,” said Dr. Paul Offit, a voting member of the Vaccines and Related Biological Products Advisory Committee, which is scheduled to review Pfizer’s vaccine on Dec. 10. “I don’t know what data the U.K. was working with. I know when data is submitted to the FDA, it’s voluminous,” said Offit, also director of the Vaccine Education Center at Children’s Hospital of Philadelphia. “When you talk about a 44,000-person trial, that’s a lot of clinical data.” He said when Merck submitted its data from its 70,000-person rotavirus vaccine trial, the pages that were generated could have exceeded the height of the Sears Tower. That building, now known as Willis Tower, is a 1,450-foot skyscraper in Chicago. “The point being: It’s a lot of data,” Offit said. Pfizer submitted its Covid vaccine data to the FDA on Nov. 20. The FDA has indicated it would authorize a vaccine that’s safe and at least 50% effective. The flu vaccine, by comparison, generally reduces people’s risk of getting influenza by 40% to 60% compared with people who aren’t inoculated, according to the Centers for Disease Control and Prevention. The agency’s review of the vaccine is expected to take a few weeks, and public health officials expect that the first doses of the vaccine could be distributed in as little as two weeks. Offit said he doesn’t think a U.S. authorization about a week after the U.K. makes a difference when you’re talking about vaccinating hundreds of millions of people. Immunizing everyone who wants a vaccine is likely going to take more than a year, he added. Additionally, the U.K. has been sharply criticized for approving Pfizer’s vaccine so quickly. Dr. Anthony Fauci, the nation’s leading infectious disease expert, told Fox News that the U.K. did not review Pfizer’s data “carefully.” » Subscribe to CNBC TV: https://cnb.cx/SubscribeCNBCtelevision » Subscribe to CNBC: https://cnb.cx/SubscribeCNBC » Subscribe to CNBC Classic: https://cnb.cx/SubscribeCNBCclassic Turn to CNBC TV for the latest stock market news and analysis. From market futures to live price updates CNBC is the leader in business news worldwide. The News with Shepard Smith is CNBC’s daily news podcast providing deep, non-partisan coverage and perspective on the day’s most important stories. Available to listen by 8:30pm ET / 5:30pm PT daily beginning September 30: https://www.cnbc.com/2020/09/29/the-news-with-shepard-smith-podcast.html?__source=youtube%7Cshepsmith%7Cpodcast Connect with CNBC News Online Get the latest news: http://www.cnbc.com/ Follow CNBC on LinkedIn: https://cnb.cx/LinkedInCNBC Follow CNBC News on Facebook: https://cnb.cx/LikeCNBC Follow CNBC News on Twitter: https://cnb.cx/FollowCNBC Follow CNBC News on Instagram: https://cnb.cx/InstagramCNBC https://www.cnbc.com/select/best-credit-cards/ #CNBC #CNBCTV