LONDON — The United Kingdom has become the first Western nation to begin vaccinating its citizens with a Covid-19 shot outside of clinical trials — a landmark moment in the coronavirus pandemic. The first Briton to get the Pfizer/BioNTech vaccine — 90-year-old Margaret Keenan — received the first of two doses at 6:31 a.m. local time on Tuesday at University Hospital in Coventry, less than a week after the UK became the first country to approve it. Keenan, who turns 91 next week, said she felt "privileged" to be first to get the shot. "It"s the best early birthday present I could wish for because it means I can finally look forward to spending time with my family and friends in the New Year after being on my own for most of the year," she said, according to a statement released by the UK"s National Health Service (NHS). William Shakespere, 81, known to friends as Bill, was the second person to get a COVID-19 vaccine at the University Hospital in Coventry on Tuesday. Shakespeare, a patient on the hospital"s frailty ward, sat with his grandchildren"s artwork nearby as he received the jab. In London, George Dyer become one of the first people in the capital to get the jab at Croydon Health Services while nurse Joanna Sloan was the first person in Northern Ireland to receive the vaccine. The logistical challenges of manufacturing and distributing tens of millions of vaccines mean the roll-out will be gradual, with the most vulnerable people and health care workers first in line. May Parsons, the nurse who administered the first jab, said she was honored to be involved in the program. "The last few months have been tough for all of us working in the NHS, but now it feels like there is light at the end of the tunnel," she said. The UK has ordered 40 million doses of the vaccine, but only 800,000 shots will be available as part of the first wave that began on Tuesday. Because the vaccine requires two doses, administered at least three weeks apart, the UK will have enough shots to vaccinate roughly a third of the country"s population. The country has also ordered 7 million doses of the Moderna vaccine, which could be approved for emergency use in the UK within the next few weeks. There will be 50 vaccination hubs in hospitals across England and dozens more across Wales and Scotland. In England, the first wave of vaccinations will only be administered in hospitals. Wales and Scotland have yet to specify the types of locations they plan to have administer the vaccine. Keenan and the others will have to go back for the second dose in three or four weeks" time. According to the government"s guidance, each vaccinated person will receive a credit card-sized vaccination document with details of their next appointment. Seven to 10 days after the second dose, she should be protected against the virus. UK Health Secretary Matt Hancock called the beginning of the vaccination program a "big moment in scientific endeavor" on Tuesday, saying that the vaccine "can start to heal this disease right across the world, and protect people everywhere." In an interview with Sky News on Tuesday morning, Hancock said there was still "an enormous amount of work to do," but that it may be possible to lift the UK"s coronavirus restrictions in the spring if enough people have been vaccinated by then. He urged the public to "hold our nerve and stick together and follow the rules." While the UK"s immunization program started with a big bang on Tuesday, the vaccine remains off limits to the vast majority of people. For now, it is available by invitation only for those age 80 and over, care homes staff and front line health and social care workers. Care home residents were also expected to be prioritized, but the government said last week that this won"t happen immediately. The NHS said in a statement on Tuesday that vaccine centers would be set up in venues including sporting venues and conference centers to treat large numbers of patients once further supplies of vaccine become available. Hari Shukla, 87, from Tyne and Wear in England"s north east, was due to be one of the first to get vaccinated at a hospital in Newcastle later on Tuesday. Ahead of the jab, he thanked the UK"s National Health Service for its work throughout the pandemic, saying that its staff "have a heart of gold." "I"m so pleased we are hopefully coming towards the end of this pandemic and I am delighted to be doing my bit by having the vaccine, I feel it is my duty to do so and do whatever I can to help," Shukla said in a NHS statement. The Pfizer/BioNTech vaccine needs to be stored at around minus 70 degrees Celsius (minus 94 degrees Fahrenheit), which makes its distribution difficult. Moderna"s vaccine, if approved, could be a more practical option for the care homes, as it can be kept at minus 20 degrees Celsius (minus 4 degrees Fahrenheit). — Courtesy CNN