A useful set of figures would be what proportion of trace-and-test trails were successfully pursued to conclusion, ie:
In the UK, around 40,000 infections being detected per day caused half a million people they’d been in proximity with to be contacted (“pinged”) by trace-and-test. With a testing capacity of, say, 100,000 per day it’d take 5 days to test them all; meanwhile, the positives among them are passing it on, creating yet more to follow up. Viral spread races ahead of trace-and-test.
But if, say, around 20 positives are found in a day, and on average they each had 20 encounters, that’s just 400 to follow up. Of those 400, the negatives are “trail closed”. The positives lead to further tests, but that’s easy – with a testing capacity of 100,000 per day, even speculative contacts of those “tested today but results pending” can be tested that same day. Tracing, testing and isolation can get ahead of infection, so spread is choked off.
It’s like fire; the sooner you fight it the less of it there will be to fight. Get ahead. And then make sure you stay ahead.
So maybe that’s the difference in Germany; maybe their trace-and-test is still ahead of infections, with all trails pursued until they find 100% negatives. In the UK, we can’t even follow all the trails because we have far too many. The percentage closure rates of trace-and-test would tell us, but I don’t know where to find those figures.