Reason has followed up on an Sky News story with an article by Ronald Bailey July 1 reporting studies in Sweden and Germany that show that many people have T-cell response that will protect them from coronavirus exposures (except maybe very large ones).
Sweden approaches with caution: it is not clear yet whether you have protection from cellular immunity alone after antibodies die off. It is common with other infectious agents that you do, or that cellular immunity makes your symptoms from a subsequent case trivial.
This may be interesting to protesters and journalists who march with them to film them. Unlike people going to bars, birthday house parties and church services, protesters seem to be staying on good health for the most part. Most have worn masks. But the scream and holler a lot. I have heard of cases where people say they have tested negative by PCR despite marching in these events. Antibody tests aren’t as common but it is likely many have antibodies for a while.
I notice this with my own body aging. I stopped having strep throats after having them 2 or 3 times in my 40s. I’ve had norovirus once (in 2009) in the past 20 years, whereas as a youngster it was common. A serious deep dental bone infection in 2004 never returned. All of these suggest cellular immunity, not antibodies. But cellular immunity can also drive cytokine storms. The important thing with the coronavirus is that the response needs to be proportional to need right after infection. Genes and blood type may matter.
We should be studying the T-cell response of people with asymptomatic or “mild” COVID, and with people who test negative on PCR but who have at least one positive antibody test. This may suggest ways of designing better drugs as prophylactics or help with vaccines.
An earlier video from Medcram explains a particular hooker: Sars-Cov2 can actually invade a T4 cell but cannot reproduce inside it (unlike HIV). Also another possible complication if antibody dependent enhancement (ADE) from IgM antibodies. PeakProsperity has mentioned this, and I'll look further.
Update: July 10
Swedish study (in pre-print) examines T-cell immunity, which is more like a "resistance" rather than absence of infection. That's why the 4 minor coronaviruses are harmless to humans with normal cellular immunity. Humans have had time to learn to deal with them.