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Severity rate and fatality rate in 6th wave
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Graduate School of Economics, Faculty of Economics, The University of Tokyo
Background
■If we would like to consider how to respond to the sixth wave from the perspective of “balancing infectious disease control and socioeconomic activities,” it is important to predict the rate of serious illness during the sixth wave.
■A guideline is to “continue social, economic, cultural, and educational activities as much as possible while avoiding a strain on the medical system.”
■Accurate prediction of the serious illness rate will lead to accurate prediction of when straining on medical system is likely to occur.
■Note that there is also a guideline that “a relative emphasis on infection control is good for the economy in the medium to long term.”
■Fujii-Nakata analysis before the start of vaccination: https://covid19outputjapan.github.io/JP/resources.html
■Note that while this could be said under a variety of conditions before vaccination began, it is not necessarily a robust guideline in the situation after the second vaccination has been completed.
■Post-vaccination world: Long-term Outlook for COVID-19 Infection and Economic Activity
■https://covid19outputjapan.github.io/JP/files/FujiiNakata_LongTermOutlook_20210831.pdf
Analysis
■This document quantitatively summarizes the determinants of the rate of serious illness in the sixth wave.
■Estimate how the following 4 factors contribute to the “average rate of serious illness.”
■Percentage of positive cases who received 2 vaccinations
■Percentage of elderly among those who are tested positive
■Prevention rate of serious illness from Omicron variant for those who received 2 vaccinations
■Intrinsic rate of serious illness of Omicron variant
■Monitor how much the rate of serious illness decreases during the sixth wave compared to the fifth wave.
■3 scenarios are presented
■Performed similar analysis for mortality rate
3 scenarios (serious illness rate)

Results (serious illness rate)

■Contribution (Tokyo, basic scenario)
■Fifth wave: 0.66%
■+ Percentage of people who received 2 vaccinations: 0.36% (-45%)
■+ Percentage of elderly people: 0.42% (+17%)
■+ Intrinsic rate of serious illness of Omicron variant: 0.13% (-70%)
■+ 2 vaccinations to prevent serious illness (= sixth wave): 0.15% (+16%)
3 scenarios (mortality rate)

Results (mortality rate)

■Contribution (Tokyo, basic scenario)
■Fifth wave: 0.31%
■+ Percentage of people who received 2 vaccinations: 0.19% (-40%)
■+ Percentage of elderly people: 0.27% (+43%)
■+ Intrinsic mortality rate of Omicron variant: 0.081% (-70%)
■+ 2 vaccinations to prevent mortality (= sixth wave): 0.094% (+16%)
Serious Illness Rate During Fifth Wave
Tokyo

Definition of seriously ill patients: ventilator treatment and ECMO
https://www.bousai.metro.tokyo.lg.jp/_res/projects/default_project/_page_/001/015/652/64/20210930g.pdf
Osaka

Definition of seriously ill patients: ventilator treatment, ECMO, and ICU in critical care beds (Note that this definition is broader than that of Tokyo)
https://www.pref.osaka.lg.jp/attach/38215/00413702/1-1kansenzyoukyou1222.pdf
Percentage of positive cases who received 2 vaccinations

https://www.mhlw.go.jp/content/10900000/000853141.pdf
*Created by the author based on the table on p. 59
https://www.pref.osaka.lg.jp/attach/38215/00415304/1-1-0107.pdf
Percentage of elderly among those who are tested positive

Created by the author based on the following data set
https://catalog.data.metro.tokyo.lg.jp/dataset/t000010d0000000068
https://www.pref.osaka.lg.jp/attach/38215/00415304/1-1-0107.pdf
Efficacy of 2 vaccinations in preventing serious illness: Tokyo

Serious illness rates were calculated for the 2 groups of aged under 60 (aged 30s and under as well as 40s and 50s) and aged 60 and over dividing the number of positive cases by the number of seriously ill patients based on the table on slide p.5. The efficacy of preventing serious illness from the Delta variant was assumed to be 30% based on data from Osaka Prefecture.
Efficacy of 2 vaccinations in preventing serious illness: Osaka

After 2 groups of those aged under 60 (aged 20s-30s as well as 40s-50s) and aged 60 and over are divided into those who had received 2 vaccinations and those who have not received yet, serious illness rates were calculated for each group dividing the number of positive cases by the number of seriously ill patients based on the table on slide p.6.
Serious Illness Rate During Sixth Wave
Percentage of positive cases who received 2 vaccinations

Created by the author based on the Tokyo Metropolitan Government's press release (*Percentage excluding those with unknown vaccination history)
https://www.fukushihoken.metro.tokyo.lg.jp/hodo/saishin/
Percentage of elderly among those who are tested positive

Created by the author based on the following data set
https://catalog.data.metro.tokyo.lg.jp/dataset/t000010d0000000068
Intrinsic rate of serious illness of Omicron variant
Efficacy of 2 vaccinations in preventing serious illness from Omicron variant

“Conditional efficacy of preventing serious illness”: The degree to which vaccination reduces the probability of serious illness after infection (Calculation method is based on data from Imperial College London)
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/984688/S1228_Imperial_Evaluating_the_Roadmap_out_of_Lockdown_Step_3.pdf
Mortality Rate during Fifth Wave
Efficacy of 2 vaccinations in preventing mortality: Tokyo

Mortality rates were calculated for the 2 groups of aged under 60 (aged 30s and under as well as 40s and 50s) and aged 60 and over dividing the number of positive cases by the number of mortalities based on the table on slide p.26. The efficacy of preventing mortality from the Delta variant was assumed to be 30% based on data from Osaka Prefecture.
Efficacy of 2 vaccinations in preventing mortality: Osaka

After 2 groups of those aged under 60 (aged 20s-30s as well as 40s-50s) and aged 60 and over are divided into those who had received 2 vaccinations and those who have not received yet, mortality rates were calculated for each group dividing the number of positive cases by the number of mortalities based on the table on slide p.6.
Mortality Rate during Sixth Wave
Efficacy of 2 vaccinations in preventing mortality from Omicron variant

“Conditional efficacy of preventing mortality”: The degree to which vaccination reduces the probability of mortality after infection (Calculation method is based on data from Imperial College London)
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/984688/S1228_Imperial_Evaluating_the_Roadmap_out_of_Lockdown_Step_3.pdf
■Analysis update and Zoom briefing on Tuesdays: https://Covid19OutputJapan.github.io/JP/
■Reference materials: https://covid19outputjapan.github.io/JP/resources.html
■Zoom briefing video: https://covid19outputjapan.github.io/JP/recording.html
■Economic Seminar Series
■https://note.com/keisemi/n/n9d8f9c9b72af
■https://note.com/keisemi/n/n7f38099d0fa2
■https://note.com/keisemi/n/nd1a6da98f00e
■https://note.com/keisemi/n/n430f8178c663
■Papers available at:https://link.springer.com/article/10.1007%2Fs42973-021-00098-4
■Twitter: https://twitter.com/NakataTaisuke
■Questions, requests for analysis, etc.
■taisuke.nakata@e.u-tokyo.ac.jp