A retired British shop clerk received the first shot in the country’s Covid-19 vaccination program Tuesday, the start of an unprecedented global immunization effort intended to offer a route out of a pandemic that has killed 1.5 million.

The Associated Press reports that Margaret Keenan, who turns 91 next week, got the shot at 6:31 a.m. on what public health officials have dubbed “V-Day.” She was first in line at University Hospital Coventry, one of several hospitals around the country that are handling the initial phase of the United Kingdom’s program. As luck would have it, the second injection went to a man named William Shakespeare, an 81-year-old who hails from Warwickshire, the county where the bard was born.

The U.K. is the first Western country to start a mass vaccination program after British regulators last week authorized the use of a Covid-19 shot developed by U.S. drugmaker Pfizer and Germany’s BioNTech. U.S. and European Union regulators may approve the vaccine in the coming days or weeks, fueling a global immunization effort.

Britain’s program is likely to provide lessons for other countries as they prepare for the unprecedented task of vaccinating billions of people. U.K. health officials have been working for months to adapt a system geared toward vaccinating groups of people like school children and pregnant women into one that can rapidly reach much of the nation’s population.

Amid the fanfare that greeted Britain’s first shot, authorities warned that the vaccination campaign would take many months, meaning painful restrictions that have disrupted daily life and punished the economy are likely to continue until spring.

Other vaccines are also being reviewed by regulators around the world, including a collaboration between Oxford University and drugmaker AstraZeneca and one developed by U.S. biotechnology company Moderna.

Britain has received 800,000 doses of the Pfizer vaccine, enough to vaccinate 400,000 people. The first shots will go to people over 80 who are either hospitalized or already have outpatient appointments scheduled, along with nursing home workers and vaccination staff. Others will have to wait their turn.

Britain is the first country to deliver a broadly tested and independently reviewed vaccine to the general public. On Saturday, Russia began vaccinating thousands of doctors, teachers and others at dozens of centers in Moscow with its Sputnik V vaccine.

China has also begun giving its own domestically made shots to its citizens and selling them abroad. But those products are being viewed differently because neither countries’ vaccines have finished the late-stage trials scientists consider essential for proving that a vaccine is safe and effective.