It is very tempting to believe in the highest estimate of the Oxford study - iirc they have a range -
which would bring an early and much less severe resolution of the crisis
However, the evidence does not seem there:
The UK test a very small number of people, those with more severe sympoms that make COVID a likely diagnosis
Even those tests have fewer positives than 50%
Germany are testing about 500,000 per week and have a total of 100,000 cases,
so we are also assuming here that only a small % have had COVID
and we are in for a long haul.
Hence the planned German study of repeatedly testing the same 100,000 people, as soon as a reliable test for immunity is available
This will show both the baseline immunity level and how it grows