The UK became the first country today (Dec. 8) to use Pfizer and BioNTech’s vaccine to inoculate people against Covid-19.

Britain first approved the vaccine for emergency use on Dec.2. It has purchased 40 million doses, which it says is enough to vaccinate about a third of its population. Here’s guidance from the Joint Committee on Vaccination and Immunisation, a group of experts that advises UK health departments on vaccines, on the first people to receive the jab: