The idea that there is 'no immunity to SARS-COV-2' may be flawed. I found this article in the BJM very interesting re the importance of memory T-cells:
Covid-19: Do many people have pre-existing immunity?
Published 17 Sept 2020
An excerpt:
t least six studies have reported T cell reactivity against SARS-CoV-2 in 20% to 50% of people with no known exposure to the virus.
In a study of donor blood specimens obtained in the US between 2015 and 2018, 50% displayed various forms of T cell reactivity to SARS-CoV-2. A similar study that used specimens from the Netherlands reported T cell reactivity in two of 10 people who had not been exposed to the virus.
In Germany reactive T cells were detected in a third of SARS-CoV-2 seronegative healthy donors (23 of 68). In Singapore a team analysed specimens taken from people with no contact or personal history of SARS or covid-19; 12 of 26 specimens taken before July 2019 showed reactivity to SARS-CoV-2, as did seven of 11 from people who were seronegative against the virus.8 Reactivity was also discovered in the UK and Sweden.
Though these studies are small and do not yet provide precise estimates of pre-existing immunological responses to SARS-CoV-2, they are hard to dismiss, with several being published in Cell and Nature. Alessandro Sette, an immunologist from La Jolla Institute for Immunology in California and an author of several of the studies (box 1), told The BMJ, “At this point there are a number of studies that are seeing this reactivity in different continents, different labs. As a scientist you know that is a hallmark of something that has a very strong footing.”
and:
“At the start of the pandemic, a key mantra was that we needed the game changer of antibody data to understand who had been infected and how many were protected,” two immunologists from Imperial College London wrote in a mid-July commentary in Science Immunology. “As we have learned more about this challenging infection, it is time to admit that we really need the T cell data too.”
Theoretically, the placebo arm of a covid-19 vaccine trial could provide a straightforward way to carry out such a study, by comparing the clinical outcomes of people with versus those without pre-existing T cell reactivity to SARS-CoV-2. A review by The BMJ of all primary and secondary outcome measures being studied in the two large ongoing, placebo controlled phase III trials, however, suggests that no such analysis is being done.
www.bmj.com/content/370/bmj.m3563
We really need more data on the role of T-cell immunity, it could turn out to be a game-changer.