It took me about 6-8 weeks Malc, but once the fatigue lifted it took no time at all to get back up to speed. My heart rate doesn't sit quite as low on my runs any more, but I hope that will come back long term.
It's really noticeably burning through work (including families-of) at the moment. This despite most people still working from home most of the week. I assume the variant that has been in the news.
I tested positive just before going to get COVID and flu jabs the other week (and had a much shittier time of it than last time around), but was plague free for the rebooking this evening. Apparently it's now a modified vaccine focusing on the current variant and less likely to work against the outgoing ones.