Analysis of the number of school and class closures

■Increase in class closures and school closures in association with the spread of infections

■Analysis of closures of daycare centers, etc.: “Analysis of the Number of Closures of Daycare Centers, etc.” (Chiba, Okamoto)
■This document analyzes trends in the closure of elementary schools, junior high schools and high schools, and the closure of classes.

■We analyzed the relationship between vaccinations and school closures or class closures based on the data of municipalities.
■As of the end of January 2022, vaccinations have largely not progressed only among children under 10 years old.
■The vaccination rate among children under 10 years old was 0.0% in all prefectures.
■Among children 10 years old or older, the second vaccination rate was 61.2% nationwide (51.8%-67.9% by prefecture).
■As a result of DID estimates, the possibility is suggested that children under 10 years old being almost completely unvaccinated may have caused the rapid increase in the number of elementary school closures (compared to junior high and high schools).
■If vaccinations of elementary school students had advanced to the same level as those of junior high and high school students, it is possible that the number of school closures and class closures in the sixth wavecould have been reduced by about 40%.

■Analysis of changes in the number of days of school closures
■Ministry of Education, Culture, Sports, Science and Technology guidelines of February 2 reduced the rough guide for the number of days of a school closure.
■In fact, there are municipalities where the number of days of school closures has increased (similar to the closure of daycare centers, etc.).

Results of a Survey on Temporary School Closures Due to the Impact of COVID-19 (as of February 9)
https://www.mext.go.jp/content/20220218-mxt_kenshoku-000006590_1.pdf

■Before vaccinations started, the rate of increase in the number of closures of schools and closures of classes was equivalent at elementary schools versus middle and high schools. (Parallel trend assumption)

■Before vaccinations -> start of vaccinations ~ transition period -> after vaccinations became widespread among each generation: following the three periods of the sixth wave, the difference in the number of closures of schools and closures of classes expanded.

We think that the result of subtracting the difference before the start of vaccinations from the difference (logarithm) in the number of closures of schools after December 2021
is entirely due to the difference in vaccination rates (common shock assumption).

The difference is about 0.228 -> 100.228 (= about 1.69)

Vaccination effect => 1 - 1 / 1.69 = 0.41 = about 40%
(Reference: Second vaccination rate for children 10 to 19 years old in Osaka Prefecture = 52.7% [as of February 8])

During the sixth wave, if vaccinations of elementary school students had advanced to the same level as those of junior high and high school students, it is possible that the number of school closures and class closures could have been reduced by about 40%.

■Note that these figures are based on the two following assumptions.

1.Parallel trend assumption:
If all children were not vaccinated, the rate of increase (approximately equal to the difference between the common logarithms) for both would be equal.e.g.) If the number of closures of elementary schools is twice as high in winter than in summer, (and if junior high school students were not vaccinated,) the number of closures of junior high schools should also double.

2.Parallel trend assumption:
There are no factors other than vaccination that would make the difference. e.g.) This assumption would not be established if the standard for the closure only of junior high schools was raised during the sixth wave.

Note that the parallel trend assumption before the start of vaccinations is not valid in Fukuoka City.

In Fukuoka City as in Osaka City (after the start of vaccinations), the difference in the number of closures of schools and closures of classes expanded gradually.

■The rough guide*1 for the number of days of closures of schools established by the Ministry of Education, Culture, Sports, Science and Technology is for an upper limit of about five days from February 2.
■This is linked to the general isolation period for close contacts.*2

※1　https://www.mext.go.jp/content/20220113-mxt_kouhou01-000004520_1.pdf
https://www.mext.go.jp/content/20220202-mxt_kouhou01-000004520_2.pdf
※2　https://www.mhlw.go.jp/content/000889667.pdf

■There were some municipalities where the number of days of closures of classes increased from February 2.
■Even if they aimed to shorten the period of isolation of positive cases, there may have been cases where shortening was not possible in reality due to delays in testing or the availability of resources, etc.
*p < 0.10, ** p < 0.05, ***p < 0.001
Obtained from the websites of each municipality

*p < 0.10, ** p < 0.05, ***p < 0.001
Obtained from the websites of each municipality

*1 Average number of days of closures of classes in Fukuoka City from January 14 to 20
*p < 0.10, ** p < 0.05, ***p < 0.001
Obtained from the websites of each municipality

*1 Average number of days of closures of classes in Fukuoka City from January 14 to 20
*p < 0.10, ** p < 0.05, ***p < 0.001
Obtained from the websites of each municipality

※In both municipalities, the vaccination rate for children under 10 years old is 0.00%.

*This is the aggregate for closures of schools and closures of classes (including closures of grades).
*Subjects were excluded where school category was “Unknown.”
*The figures for Osaka City are as of February 16, 2022 and those for Fukuoka City are as of January 21, 2022.