US study shows COVID vaccines' efficacy wanes even more than thought

There have been quite a few studies looking at the decline on effectiveness in COVID-19 vaccines over time, but none have been quite as depressing as a recent study of 780,000 US veterans.

This study, published in the journal Science, shows a huge drop in efficacy in all the vaccines in the six months between March and the end of September. Two doses of Moderna's effectiveness fell from 89% to just 58%; Pfizer/BioNTech's effectiveness fell from 87% to 45%; and the single dose Johnson & Johnson vaccine's efficacy fell from 86% to a paltry 13% over the same period. AstraZeneca vaccines have not been used in the USA, but you can probably assume that its performance will be more similar to the Johnson & Johnson shot than to the mRNAs.

The study only looks at US veterans, generally older and largely men, but this nevertheless seems to be a real wake-up call, and will only serve to increase the clamour for third doses after six months, which many developed nations are already embarking on.