Not blaming the staff, just that SG doesn't seem able to plan ahead or have appropriate strategies in place for the demographics in advance
To be fair, it's the biggest medical issue they've ever faced, they are dealing with vaccine supplies not being consistent (through no fault of their own) and they are having to manage ensuring people get the same kind of vaccine that they had previously within a narrow time frame.
This is no small feat. And the UK have vaccinated a higher percentage of the population than almost anywhere else in the world. There are, I believe, only two countries that have done better with their vaccination programmes, one of which has a population of 360,000 people, the other has less than 40 million.