There is a delay in administering the vaccine because of, among other things, a delay in recruiting a voluntary workforce, many of whom are ex-employees of the NHS. This also applied earlier in the acute stage of the illness, and may now be occurring once more as case rise rapidly. This has a huge knock-on effect on the rest of the NHS, particularly the cancellation of millions of routine appointments, investigations, procedures and operations such that the diagnosis and treatment of serious diseases have been delayed.
If retired or resigned members of the NHS workforce could be registered as a voluntary reserve resource, with occasional online retraining or re-certification as necessary, they could be rapidly deployed in the case of emergencies such as the pandemic, without the huge, cumbersome and wasteful bureaucratic exercise which has seen people struggling with apparently irrelevant online training to be allowed to do relatively simple tasks such as vaccination. Whether they could be organised to a sufficient extent to undertake more complex tasks such as screening, activities closer to the specialist activities they were responsible for while employed is a slightly different question, and would require more rigorous supervision and governance.
Finally, many of these people might not have retired/resigned had the NHS learned how to manage careers in a way that recognises that professionals who love their jobs, but are exhausted may want to gradually reduce their responsibilities from age, say, 55 onwards.