The U.K. will allow emergency use of the COVID-19 vaccine made by Pfizer and BioNTech.
The announcement makes Britain the first Western country to greenlight a vaccine.
The U.K. says it's already ordered enough doses to fully vaccinate 20 million people.
Pfizer said last month that its vaccine candidate is up to 95% effective.
U.S. health authorities are also reviewing the vaccine, but have not granted approval yet.