Discussion
There is increasing empirical evidence that our current view on contagiousness and hazard potential of COVID 19 is heavily biased by test strategy and selective sampling. Just to name a few:
The “true” basic reproduction rate of SARS-COV-2 probably never was anywhere close to the dimension of 2.5 to 3, as it is still reported in official information . However, model simulation studies have been typically fitted exactly to these biased numbers. For SIR (Susceptible – Infected – Recovered) models, due to lack of representative data we do not have any valid basis for estimating the number of infected nor the number of recovered patients, nor the susceptible population. There is emerging evidence on cross-immunity with harmless Corona viruses that may already be in the region of 30 to 40 percent or even 80 percent according to some very recent results on T-cell activity . This would for example explain findings like couples sharing the same cabin on a cruise ship or living with a symptomatic COVID patient in the same household but not getting infected. It would also fit to the fact that we see the infection rate in Sweden subside, although they should not have had much more than 15 percent of their population contracting the virus so far, which would not be sufficient for herd immunity.
In summary, public surveillance data as published by the RKI do not confirm a strong impact of public health measures on SARS COV 2 spread in the German population. Specifically, public mobility as an indicator of compliance with social distancing rules seems to be influenced by published infection rates rather than being a moderating factor for infection. Data from the initial phase of the pandemic could be heavily biased and thus provide a severely distorted picture of contagiousness and risk of severe course of disease. Model simulations building on these data will likewise be biased to exaggerated outcomes. There is an ongoing need for solid and large-scale epidemiological studies that not only address currently active infections but also consider resent findings on t-cell based immunity and cross-immunity. The demand for more empirical data has been raised early e.g. by the German society for evidence-based medicine, and it is still valid. Rather than focusing on infection containment in the broad population it might be more reasonable to focus on correctly identifying and protecting the high-risk population, which is probably much smaller than currently perceived.
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