RE: Most of the World’s Vaccines Likely Won’t Prevent Infection NYT20 Dec 2021 07:12
Here are the thought from Harvard on this theory of comparing severity between populations and also the media trumpeting of ‘viruses always evolve to become milder’ rubbish.
“Viruses have no intrinsic tendency to evolve towards lower virulence; evolution simply selects those that excel at making more of themselves. In an illness like COVID-19 where the vast majority of spread occurs prior to severe disease, severity is likely not directly selected upon at all. HIV is a classic example of a successful pathogen despite being fatal in >99% of cases if untreated. Indeed, previously observed variants of SARS-CoV-2 with enhanced transmission (Alpha and Delta) appear to have greater intrinsic severity10-13. While the lower observed IFR in the early weeks of the Omicron wave in South Africa is better than the alternative, the most likely explanation lies in increased immunity among those being infected; more time and careful comparisons controlling for age, prior immunity, detection bias, lag period, hospital capacity, and numerous other factors will be required to infer anything about intrinsic virulence. Our collective intuition on how population-level IFR relates to intrinsic severity of a variant needs to be recalibrated over time as immunity accrues, and far more so with a variant as immune-evasive as Omicron.”
https://cdn1.sph.harvard.edu/wp-content/uploads/sites/2623/2021/12/21_Hanage_Bhattacharyya_Challenges-in-assessing-Omicron-severity_HCPDS-Working-Paper-Volume-21_No-10-1.pdf