Disclosure request items

The requested data fields from local governments:

• Date of birth or age at the time of data extraction
• Gender
• Date of death if deceased
• Move-Out-Date when relocation from a residence
• Move-In-Date when relocation to a residence
• Date of vaccination administered and its lot number

About the "Whole country" Option

The "Whole country" option in the drop-down list on the lot summary page does not necessarily include all prefectures. Only those prefectures registered in the database are included in the summary.

About the "Prefecture" Option

The "Prefecture" option in the drop-down list on the lot summary page does not necessarily include all cities, wards, towns, and villages in the prefecture. Only those municipality within the prefecture that are registered in the database are included in the summary.

About Classification by Generation

The naming convention for age group classification is youth, working generation, and elderly, with the ages of 20 and 65 used as cutoff points for youth and elderly respectively. However, in this project, the cutoff point for elderly is set at 70 years old. This is due to disclosure practices of local governments. For example, “age groups" classification in many cases are in increments of 10 years, such as 0-9 years or 10-19 years, etc. Thus, since the conventional cutoff is set at 65 years old, the calculation categories will not be consistent with other municipalities, rendering cross regional comparisons difficult. Therefore, for ease of comparison, this site has set the cutoff point between elderly and working generation at 70 years old.

Inconsistency in Lot Number Notation

As a general rule, lot numbers will not be excluded or altered from the provided data even if they contain typographical errors. However, lot numbers that vary from the standardized "half-width, uppercase, no spaces” modified for consistency.

About the Age

As a general rule, we use the "age at the time of data extraction" for age. For deceased individuals, we inquire with local governments about their "age at death." Ideally, knowing the date of birth would allow us to calculate the accurate "age at time of vaccination" and "age category." However, in practice, each local government uses different disclosure formats, resulting in a mixture of age, date of birth, and increments of 10 or 5 years. Therefore, if an age category is disclosed, we use that category, and if individual ages are known, we use that value as is. Because the observational period for vaccination is limited to a maximum of approximately three years, only a few percent of cases cross age categories (e.g., 20, 65, 70, etc.). Therefore, we strike a balance between accuracy and efficiency when compiling data in this manner.

Handling of Single-Digit Vaccination Totals

In the summary table, Top 100 Mortality Rates by Lot, lots with 5 or fewer vaccinations in the "Total" with an option of "Whole country" are not displayed. However, included in the total count. The reasoning behind this is that of the more than 10 million vaccinations recorded nationwide, lots with only a single-digit number of vaccinations are likely to be typos or input errors. Also, if such lots were displayed at the top of the list, it would be difficult to display the overall trend of the statistics.

Time from Vaccination to Death

In the table of "Top 100 Mortality Rates by Lot," options in the drop-down list for "Time from vaccination to death" include "Within 1 month," "Within 2 months," "Within 6 months," and "Within 1 year;" however, the actual calculation is based on the number of days as listed below:

• Within 1 month: Within 28 days
• Within 2 months: Within 63 days
• Within 6 months: Within 182 days
• Within 1 year: Within 364 days

This is because the number of days after vaccination to death is calculated in 7-day increments and then rounded up or down. For example, those who died on the 29th or 30th day after being vaccinated will be in the "within two months" and not counted in "Within one month"

About the Data Collection Period

Freedom of information act request seeks "information on all subjects (including those who have not been vaccinated) from the month the COVID-19 vaccine was administered to the date of this disclosure request". However, in practice, many local governments have not disclosed information beyond the end of March 2024, claiming that operation of the VRS (Vaccination Record System) had ended at that time.

However, there are cases where data has been stored in some form after the end of the VRS and death records of those unvaccinated have been available into 2025. The Lot Count page has data that covers the period (in the upper right) between the oldest vaccination and latest vaccination or death which is automatically extracted from the database.