So what the chart in the tweet linked above is really showing is that, within the 10-59 age band, the average unvaccinated person is much younger than the average vaccinated person, and therefore has a lower death rate. Any benefit from the vaccines is swamped by the increase in all-cause mortality rates with age.
I have mocked up some illustrative numbers in the table below to hopefully show Simpson’s Paradox in action here. I’ve split the 10-59 age band into 10-29 and 30-59. Within each group the death rate for unvaccinated people is twice as high as for vaccinated people. However, within the combined group this reverses – the vaccinated group have higher death rates on average!
I and others have written to ONS, altering them to the concerns that this data is causing. It appears from a new blog they have released that they are aware of the issue and will use narrower age bands in the next release.
Author(s): Stuart Macdonald
Publication Date: 22 Nov 2021
Publication Site: COVID-19 Actuaries Response Group