Measuring Vaccine Usefulness Without Reference to Unvaccinated Case Rates
by Dr. R.J. Booth The apparent dwindling of Covid vaccines’ effectiveness at preventing infection has been disappointing, given that vaccines against some diseases last for many years or indeed for life. Nevertheless, the prospect of booster shots topping up immunity is a welcome one, which is promised by trials conducted by the drug companies. Still, it would be interesting to see whether there is statistical evidence that this is happening in the real world as third doses get rolled out. The executive summary is that I did find some good evidence, and it has encouraged me to book a third dose. Dr. Will Jones has published articles on the Daily Sceptic which show unadjusted effectiveness rates of the vaccines, in comparison to unvaccinated people. These had worryingly strayed into significant negative territory until turning upwards more recently. But that work does not come supplied with a statistical test, and how much adjustment should be done to allow fair comparison of vaccinated and unvaccinated citizens is a fraught subject. It occurred to me that since the third doses have been deployed at different rates in the different age groups, it might be possible to observe, and analyse, a ripple of decreasing infection rates from older to younger people over the last few weeks. So I developed a statistical model for infection rates, including a value dependent on...
