> But with covid, we're still not even sure what to test for! For natural immunity, reinfection incidence (e.g. two positive PCR tests more than 100 days apart

> But with covid, we're still not even sure what to test for! For natural immunity, reinfection incidence (e.g. two positive PCR tests more than 100 days apart) would suffice? There is robust data on this now. And yes I realise the Google mandate is not about immunity per-se but the relationship between transmission rates and immunity, but this link applies to both natural and vaccine induced immunity.