i suppose because we don't have enough of the 1st vaccine to vaccinate everyone. Say, for exapmle the oxford vaccine came online next week. The NHS might want to start using that, at the same time of using the stocks up of what they already have, The frrozen one would continute o be given in hospitals, but the oxford one could be quickly nipped round to the care homes. Then uf say another came online in a few weeks, and we also had some of that, perhaps that's be shipped to anglia and those people would get that one? Clearly i have no idea how things work though :) Now they've started with the Pfizer one, are we just going to wait till we have enough for everyone, or if another came online would that start to be used as well?