Natural resistance in Italy
June 21, 2026
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320 of 364
June 21, 2026
Natural resistance in Italy
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Dr John Campbell Episodes Around June 21, 2026
Episode 320 of 364 — walk the feed in the order it was published.
22:14This episodeNatural resistance in Italy
Summary
Clear graphics from Italy, The decline of COVID-19 severity and lethality over two years of pandemic
https://www.medrxiv.org/content/10.1101/2022.07.01.22277137v1
20 to 40-fold reductions during the period of dominance of Omicron compared to the initial acute phase.
Phase 1, Ancestral
Probability of hospitalization per infection of 5.4%
Probability of ICU admission of 0.65%
Probability of death of 2.2%
Phase 5, Omicron
Probability of hospitalization, 95.1% reduction in risk
Probability of ICU admission, 97.3% reduction in risk
Probability of death, 97.5% reduction in risk
Using epidemiological and genomic surveillance data
To estimate the number of daily infections in Italy in the first two years of pandemic.
Attack rate
Ascertainment of SARS-CoV-2 infections
Phase 1 (ancestral)
NPIs
Attack rate 2.8%
Phase 2 (ancestral)
Less stringent NPIs
Attack rate 11.4%
Phase 3 Alpha variant
Mid -February 2021 to early July 2021
Alpha infected about 10.1% of the Italian population
Phase 4, Delta
Second half of 2021
Progressive relaxation of NPIs
Attack rate 17.3%
Phase 5, Omicron
End of December 2021
Attack rate, 51.1% of the Italian population became infected with Omicron
Evolution of population susceptibility
Percentage of the population susceptible to SARS-CoV-2
End of first phase, 97.5%
February 20, 2022, 13%
By February 20th, 2022
a marked proportion of individuals unprotected against SARS-CoV-2 infection can be found among vaccinated subjects,
due to the waning of vaccine protection
Evolution of COVID-19 severity and lethality
Probability of hospitalisation
Probability of ICU admission
Probability of death
Evolution of population susceptibility
Natural, post infection immunity is now the main factor reducing population sensitivity
Vaccination protection is seen to be declining
Omicron natural infection had the largest protective effect
Repeat exposure to omicron (and sub variants) is likely to have the same effect going forward.
NPIs will reduce repeat exposures
NPIs will reduce exposure to other respiratory viruses such as RSV
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