But some commenters brought up a legitimate issue with the HLH, which I'll call the unhealthy vaccinee bias (UVB): the earliest batches were given to the eldest of the elderly and the sickest of the sickly who die at higher rates regardless of what does or doesn't get injected into them. So hot lots might just be a statistical illusion that goes away once you control for pre-existing health factors, kind of like Covid vaccine effectiveness.
But in Japan, the sick and elderly didn't get the jabs first; healthcare workers did. In fact, the high-risk elderly only started getting jabbed almost two months after low-risk healthcare workers (February 17th vs April 12th 2021). This is noteworthy not just because it reminds us that the jabs were primarily sold to the population as a way to 'stop the spread' but also because it means the earliest batches delivered to Japan went to working-age people, giving us a chance to test the hot lot hypothesis free from the unhealthy vaccinee bias.
And if we were to search for evidence of, say, higher cardiovascular deaths in working-age males, where better to look than the monthly statistics for deaths due to arrhythmia and heart failure rather than just deaths reported after the jabs? The below graphs come yet again from Nagoya University's Prof Seiji Kojima.

Monthly changes in the number of deaths among men aged 10 to 49 due to heart failure from 2018 to 2022
Well, any healthcare workers who got lucky in the lot lottery and who've kept up to date with their shots will now be able to get the seventh from this week. But not to worry. I'm sure the manufacturers have fixed any and all quality assurance issues they've never publicly acknowledged.
Or maybe not.
Comment: See also: