Natural immunity is reliable, as evidenced by rhesus monkeys not getting reinfected after re-challenge and a Cleveland Clinic study showing no reinfections in hospital workers.

“so the starting hypothesis in my opinion should have been natural immunity appears reliable we don't see people getting reinfected with severe illness on the ventilator and the icu and once we start seeing that we can change the starting hypothesis but let's use the starting hypothesis that natural immunity works at least in the time that it's been around and what you had was a series of studies come out from early on two months into the pandemic rhesus monkeys were re-challenged with the virus and they did not get reinfected the cleveland clinic then came out with their big study of hospital workers who were around covett all the time and found no re-infections”