Don't ask; don't tell

About 50% of Japan's Covid deaths have unclear vaccination status

In Japan, the vaccination rate is over 80% for people aged 20 to 49 and over 90% for people over 50, reaching 98% for people between 80 and 99.

[Vaccination rate by age group: blue means 1 shot; yellow means two shots https://www3.nhk.or.jp/news/special/coronavirus/vaccine/progress/#mokuji1]

So what explains Japan’s record high numbers of reported cases and deaths?

Who exactly is getting infected and dying? To find out, let’s check the data from HER-SYS, Japan’s system for collecting and managing data on Covid cases. But before we do, we should note an interesting change made at the end of 2021 in the way vaccination status of cases is counted.

[https://www.mhlw.go.jp/content/10900000/000898602.pdf]

The sentence half in red states that “In HER-SYS, until epidemiological week 47, cases without a vaccination status input were counted as “unvaccinated,” but since week 48, they have been counted as “status unclear” [Hat-tip to https://twitter.com/BBT_Success for noticing this].

Now that’s out of the way, let’s look at the ratio of cases by vaccination status from epidemiological week 15 2021 to week 6 2022.

From week 48 onward, the ratio of “status unclear” cases has grown to 35% of cases under 65 and about 40% of cases over 65. On the other hand, the ratio of double-vaccinated cases stopped increasing around week 48 and has stayed constant ever since. So what about deaths?

In 2022 so far, apparently 50% of Covid deaths of Japanese over 65, who have a vaccination rate over 90%, have unclear vaccination status. The raw numbers of “status unclear” deaths for weeks 4, 5, and 6 are 55, 87, and 27 for people under 65 and 197, 199, and 77 for people over 65 (week 6 data is incomplete).

So what can we learn from this? If you don’t want something to be clarified, make it unclear.