We must certainly hope for the best, but also plan for the worst (tempered by realism). Whilst I certainly do cling to the hope that there will be some degree of immunity, I'm not aware of anyone actually being able to demonstrate that. It was Prof van Tam who stressed in a briefing, that we did not know if there was immunity at all, never mind if it lasted 2 months!Point taken. But we have to hope that is the case, otherwise our only realistic option is the vaccine. I think there are two issues with this. First, creation of (possible) herd immunity following society returning to increased interaction, as you say, time will tell on this. Second, the virus looks like it may be dying out in terms of how seriously it is affecting those it infects. All the reports I am reading indicates that hospitals are seeing significantly less COVID admissions.