Misleading Myocarditis Maths (Updated 9 June 2022)

Japan's Ministry of Health turns a tiny number into a big one

In October 2021, Japan’s Ministry of Health, Labour and Welfare (MHLW) decided to recommend that men under 30 take Pfizer’s vaccine rather than Moderna’s due to the latter’s higher rate of post-vaccination myocarditis and pericarditis. But the MHLW produced the below graph to stress that the risk of post-Covid myocarditis in young Japanese males is astronomically higher at 834 cases per million.

[https://www.mhlw.go.jp/content/000844011.pdf]

But before you roll up your sleeve, young man, wouldn’t you like to know the absolute numbers of reported myocarditis/pericarditis that this graph is based on? The red boxes show the actual number of reported cases of post-vaccine myocarditis/pericarditis in Japanese males (男) aged 10-19 and 20-29 up to October 3rd 2021.

And the below shows 4 reports of post-Covid myocarditis (one of whom died) from a sample of 4,798 males aged 15-39 who were hospitalised for Covid. So 1,000,000 / (4798/4) = 834.

[https://www.mhlw.go.jp/content/10601000/000844075.pdf]

So how does the top graph look when redone using the absolute numbers? (Hit-tip https://twitter.com/eishin_go)

At this point, I think the MHLW can probably remove the words “health” and “welfare'“ from the name, put considering the effort they made to turn 4 into 834, they can certainly keep the word “labour.”

Update 9 June 2022

After 8 months, Japanese TV has finally got round to questioning the MHLW’s pamphlet. Here they show the MHLW’s calculations using the four cases of post-Covid myopericarditis and 4798 hospitalised cases as the denominator, which comes to 834 cases of post-Covid myopericarditis per million infections.

And here they recalculate the numbers using the 300,000 PCR+ cases among 10-30 year old males as the denominator, which comes out to 13 cases of post-Covid myopericarditis per million infections, 64x less.

But even these numbers should be treated skeptically since there’s no control group. In contrast, an approximately 780,000-person study cohort study from Israel “did not observe an increased incidence of neither pericarditis nor myocarditis in adult patients recovering from COVID-19 infection.”

The mRNA vaccines on the other hand…

Figure.  Monthly Number of Inpatient and Emergency Department Cases of Myocarditis and Pericarditis at 40 Hospitals in the Western US

And a heterologous schedule (1 dose with BNT162b2 [Pfizer] and the other dose with mRNA-1273 [Moderna]) is especially risky.

Abbreviations: IRR, adjusted incidence rate ratio. “For a heterologous schedule (1 dose with BNT162b2 [Pfizer] and the other dose with mRNA-1273 [Moderna])…In males aged 16 to 24 years, 17 myocarditis cases occurred, with an excess number of events of 27.49 (95% CI, 14.41-40.56).”

But that didn’t stop the government from recommending it!

The Japanese fail to take Moderna fully into their hearts

The moral of this story is you can always count on the government to always count wrongly.