Ask the NHS why. They will be getting rid of those people next year.
Part of this is a study involving visits to people and monitoring. Evidence is growing that being vaccinated does reduce the chances of cross infection in groups of people in the same place. Sounds a little tentative to me, 150,000 people or places. Not clear but that effect is expected . It's what vaccination usually does.
It will also be of course be more likely to keep people at work rather than off or reduce the period of time they are off and in some cases remove the need to find replacements if they die or finish up severely hampered in some way.

