the reality seems to be the UK Government an do23 Jan 2021 10:44
whatever it feels fit, at any time, and in any given situation. The Medicines and Healthcare products Regulatory Agency (MHRA) decide all things vaccine and testing it seems. The UK Government often reference how the MHRA ids independent form them, they must be led by them etc etc .. What happens when the Pfizer/BioNTech vaccine comes out , a vaccine passed by MHRA only after rigorous research and clinical trials) where the MHRA, WHO, and the manufactures stated that a second dose of the vaccine is required six weeks after the initial vaccine dose is given.
What to the UK Government do they decoded ( with no evidence) that they will extend the period between doses to 12 weeks ( could be much longer as shortages expected). No one knows if the 2nd dose of vaccine , given so much later will have on the patient, or the effectiveness of the vaccine in protecting the person. All this confusion this goes ahead is that means that the only way anyone can find out what the status of any individual, at any time is to test them- so testing will probably go through the roof.