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Since early april I've been wondering if there's not a "black materia" of unexplained immunity to SARS-COV-2 by antibodies alone. The data did not really reconcile with the way cases developed over time. Seroprevalence was much lower than expected from SEIR dynamics. Thread:
The Swedish SEIR dynamics pointed at a larger portion of asymptomatic/mild spread than what was assumed in most other models. Sweden employed restrictions that were far from other countries in terms of strictness. But the effects were comparable to countries with similar attack.
Sweden added restrictions in sequence unlike many other countries who added them all at once. This paper suggested that some 40-60% of the population could have some form of immunity to COVID-19 already back in April. https://www.cell.com/cell/pdf/S0092-8674(20)30610-3.pdf
In May the Heinsberg study https://www.uni-bonn.de/news/111-2020 by @hendrikstreeck indicated that there was a high number of asymptomatics, it didn't infect whole families and a low IFR. It was conducted meticulously but critics didn't believe in the results and it didn't gain traction.
Roughly 40% asymptomatic and 15% symptomatic cases turn lg G negative in early convalescence. Indicating that serological studies don't show the true immunity level by this paper from June https://www.nature.com/articles/s41591-020-0965-6#Sec9
Some well known profiles in science like Karl Friston and @MLevitt_NP2013 have been indicating for a long time that there are things that do not add up with the mainstream beliefs of IFR, immunity levels. https://www.theguardian.com/world/2020/may/31/covid-19-expert-karl-friston-germany-may-have-more-immunological-dark-matter?CMP=Share_iOSApp_Other
This preprint from June indicates that about 80% of patients and people in control group have T-cell immunity while being uninfected, presumably from past "common cold" coronavirus infections. https://www.researchsquare.com/article/rs-35331/v1
Fast forward to today where a group of scientists at KI in Sweden show that immunity is higher than antibodies suggest due to T-cell mediated immunity. https://news.ki.se/immunity-to-covid-19-is-probably-higher-than-tests-have-shown?utm_source=Twitter&utm_medium=Social&utm_campaign=kasocial&utm_content=Immunity%20to%20COVID-19%20is%20probably%20higher%20than%20tests%20have%20shown
One of the biggest opponents @JoacimRocklov of the Swedish handling of the pandemic builds a picture of how SARS-COV-2 seems to be dying at 20% seroprevalence already. Explained by T-cell mediated immunity. https://theconversation.com/amp/coronavirus-could-it-be-burning-out-after-20-of-a-population-is-infected-141584#click=https://t.co/H2CyjJ1uMa
This study done this week mapped populations genomes against different types of population: non-cases, hospital cases, severe cases https://www.covid19hg.org/results/ . It found that there was a heavy spike amongst the hospitalized covid patients compared to the regular population.
Namely in the genes SLC6A20, LZTFL1, CCR9, FYCO1, CXCR6, and XCR1. What's special about these? https://pubmed.ncbi.nlm.nih.gov/31558615/ CXCR6 is shown to decrease CD8 T-cells within the respiratory epithelium. So a connection between severity of COVID-19 and lower T-cell mediated immunity.
