Run-DMC offers the 10-minute short film “Can You Catch COVID-19 Twice? How Long Does Immunity Last?”
The speaker, from the UK, gives many academic references, and the best one comes from DDB-Future, “The people with hidden immunity against Covid-19”.
He explains that the “humoral” and “myeloid” arms of the immune system themselves split into compartments. Memory T-cells are recruited like mercenaries with resumes, for their ability to fight a specific new invader. It’s almost like your T-cells had LinkedIn accounts. But the separation of functions within your immune system (a workplace concepts) is really quite elaborate, almost like the CIA.
The practical likelihood is that, even though obvious conspicuous antibodies wear off (like going bald), serviceable immunity (in immunologically healthy people) may last 1-2 years, enough time for yearly vaccines to work.
Wikipedia embed from NCI. click for attribution
Update: Aug. 25 There is one case in Hong Kong, See International Issues blog Monday Aug. 24.