The annual attack rate for original COVID — using the 850 placebo group infections in a 6,003 person-year observation window (in the original Pfizer trial) — was a rate of 14.2% spread of infection per year:
But the 20-month protection against re-infection — from those 47 million COVID infections contracted in 2020 — is estimated to be 95%:
This means that, by 2021, 14.2% of the USA (~47 million) would have had COVID, and they would have had 20 months of 95% immunity to reinfection with COVID — the equivalent of removing 13.5% of the USA from the pool of susceptibles for 2021.
But if 13.5% less people were at risk in 2021, then you expect a 13.5% drop in COVID death also. However, estimates of COVID death during 2021 are counter-intuitively 38% higher than they were in 2020:
The increased COVID death rate of 2021 was a minimum of 58% beyond expectations, given the lower pool of susceptibles in 2021 compare to 2020:
Evidence suggests that some unknown factor was introduced in 2021 — something involving at least several millions of people — and it was something which dramatically increased the susceptibility of Americans to fall prey to a COVID death (beyond the danger that they had faced in 2020).
With 13.5% less available victims, COVID deaths were 38% higher — a statistically-significant 58% increase when comparing the boundaries of 99% confidence intervals. Something made COVID in the 2021 year 60% more lethal than COVID was in 2020.
Reference
[COVID deaths by the year] — Peterson-KFF Health System Tracker. https://www.healthsystemtracker.org/brief/covid-19-leading-cause-of-death-ranking/
[US population] — U.S. Bureau of Economic Analysis, Population [B230RC0A052NBEA], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/B230RC0A052NBEA
[20 months of 95% protection against reinfection] — Nordström P, Ballin M, Nordström A. Risk of SARS-CoV-2 reinfection and COVID-19 hospitalisation in individuals with natural and hybrid immunity: a retrospective, total population cohort study in Sweden. Lancet Infect Dis. 2022 Jun;22(6):781-790. doi: 10.1016/S1473-3099(22)00143-8. Epub 2022 Apr 1. Erratum in: Lancet Infect Dis. 2022 Apr 8;: PMID: 35366962; PMCID: PMC8971363. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8971363/
[14.2% annualized attack rate] — Thomas SJ, Moreira ED Jr, Kitchin N, Absalon J, Gurtman A, Lockhart S, Perez JL, Pérez Marc G, Polack FP, Zerbini C, Bailey R, Swanson KA, Xu X, Roychoudhury S, Koury K, Bouguermouh S, Kalina WV, Cooper D, Frenck RW Jr, Hammitt LL, Türeci Ö, Nell H, Schaefer A, Ünal S, Yang Q, Liberator P, Tresnan DB, Mather S, Dormitzer PR, Şahin U, Gruber WC, Jansen KU; C4591001 Clinical Trial Group. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine through 6 Months. N Engl J Med. 2021 Nov 4;385(19):1761-1773. doi: 10.1056/NEJMoa2110345. Epub 2021 Sep 15. PMID: 34525277; PMCID: PMC8461570. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8461570/
Great post. I wonder what the 20-month reinfection rate was for people who received 1, 2, 3, 4, 5, 6, and 7 injections respectively to protect against Covid-19.