http://www.sciencemag.org/news/2021/01/could-too-much-time-between-doses-drive-coronavirus-outwit-vaccines

Visitors line up to receive an injection of a COVID-19 vaccine at a National Health Service center in Birmingham, U.K. Because of scarce vaccine, the United Kingdom has stretched the interval between doses. 

Science’s COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.