It has nothing to do with safety. If the vaccine is not as effective in over 65's as the Germans are alluding, then all of the over 65s here in the UK who have received it are less protected.
Let me have a go at this one. The suggestion above that the Oxford vaccine is not as effective in the over 65s is incorrect. What this is about is whether there is enough data to allow emergency use, given the potential risks and benefits. From a German perspective the view is that they don't have enough data for this age cohort. This may also be true of the EMA, we will find out soon. MHRA, however, have reached a different view. All three are looking at the same data, MHRA was prepared to look at other data sources to say that age didn't change effectiveness, a read across in other words. The reason we are in this position is that when the Oxford Phase III started, those initially recruited were younger for safety reasons, it was the first Phase III at the time. As Phase IIIs have come along for multiple candidate vaccines, this caution no longer applies, but this left the trial cohort skewed to younger people at the point when effectiveness was proven.