The order in which people will get the Covid Vaccination is recommended by the Joint Committee on Vaccination and Immunisation (JCVI) an decided by the Government.

Please see the JCVI/Gov UK priority groups as published on the 2nd December 2020

https://www.gov.uk/government/publications/priority-groups-for-coronavirus-covid-19-vaccination-advice-from-the-jcvi-2-december-2020