Temporal transition in the effective reproduction number in Tokyo and Okinawa
Omicron variant (generation time = 3), Other: 5 (Ratio between the delta and omicron variants or approximate for 12/22 and onward)
Trend of the effective reproduction number in Tokyo
Other than the 6th wave, moved so that their peaks match
*For the 6th wave, 3.5 was excluded from the portion of 1 or more for comparison
Reflecting on the prediction of the delta variant during year-end and new-year holidays (without the impact of the omicron variant)
Report on 11/16: 370. Report on 12/20: 140 (corrected the vaccination effect from the data of MHLW ADB)
Reproduced using the actual data of 1/11: 206 (associated with behaviors). Reproduced using the actual data of 1/18: 253
*Approximated from the ratio of patients infected with the delta variant to all positive cases. Vaccination from February. Possibility that it affects the number of seriously ill patients
Infection-prevention effect of vaccination on the omicron variant
- Infection-prevention effect of vaccination in Tokyo
Excerpted the days when the approximate proportion of the omicron variant exceeds 90%
The ratio of vaccinated people to unvaccinated people is about 4:1. Estimated that the proportion of citizens with the effect on the delta variant will become about 60% associated with temporal deterioration.
The infection-prevention effect on the omicron variant is 72.6% of that on the delta variant
Assumed to be 65–70% considering the presence of the delta variant
Future number of new positive cases in Tokyo
- Generation time: 3 days (1/1.67 compared with that of the delta variant, that is 5 days)
- Vaccination from 2/1 100,000 per day
- The changes from Cabinet Secretariat 22/1/11 were updated based on the measured values such as the occupancy of the omicron variant, flows of people, etc.
The speed of increase may decrease since the year-end and new-year holidays and the Coming-of-Age Day celebration have ended*
*This is a trend and does not guarantee any absolute value
Prediction at the end of February: 10 times? Meaning of the effective reproduction number
Effective reproduction number Green: 1.5, Red: 1.3, Blue: 1.1
Maximum number of new positive cases up to the end of February Green: 94,000, Red: 27,000, Blue: 6,300
Difference of 20% of the effective reproduction number: 3–6 times (red standard), difference of 40%, a little less than 20 times
Vaccination effectiveness per capita
Because of the deterioration of the vaccine, the infection-prevention rate per capita will not be improved significantly by infection.
Consideration of the infection condition in Okinawa
Population of Okinawa: 1.46 million
○Those who have acquired immunity
1. From infection
- Number of positive cases of the omicron variant up to 1/17 (approximate): About 16,000.
- If the proportion of asymptomatic infected people and people who were unable to take a PCR test is a little more than 4.5 times larger: The total number of infected people is 88,000
- Assuming 10 times stronger infectability = About 180,000
Infected people 6% to 12% (Rises by 3–6% per week if the level of infection remains the same)
2. From vaccination
Acquisition of immunity from vaccination (optimistic) (Defined as the value relative to unvaccinated people upon countermeasures against infection)
-> 31%
Total 37 % to 43% (At the end of the 5th wave (8/18) = About 40%*)
- The threshold may get close to the above-mentioned level
*At that time, behavioral restrictions were applied. The difference in the infectability between the omicron and delta variants and the countermeasures against infection taken by people raise the threshold.
Consideration of the infection condition in Tokyo
Population of Tokyo: 13.96 million
○Those who have acquired immunity
1. From infection
- Number of positive cases of the omicron variant up to 1/17: About 22,000.
- If the proportion of asymptomatic infected people and people who reject PCR is a little more than 4.5 times larger: The total number of infected people is 121,000
- Assuming 10 times stronger infectability = 242,000 in total
Infected people 0.8% to 1.7% (Rise by 1.4–2.8% every week assuming 50,000 people per day)
2. From vaccination
Vaccine (up to the second vaccination: optimistic) (Defined as the value relative to unvaccinated people upon countermeasures against infection)
-> 35%
36% in total (current) (If the threshold is 45 to 50%, it will take at least 3 weeks)
If booster shot starts (100,000/day), 5% will be added every week from 2 weeks later
The environment is expected to slightly improve in late February
