Two paths for Omicron

Consider the following numbers. At its Delta peak, the U.K. was recording an average of about 130 deaths per day, following from a case peak of around 47,000; with Omicron, the death total still hasn’t peaked but has reached an average of about 240, following a case peak of about 180,000. About a four-fold increase in cases has produced, so far, about a doubling in deaths, which are still rising. Even if we assume that U.K. deaths are now at their peak, those numbers would imply a rough halving of the case-fatality ratio with Omicron — a meaningful reduction but not a game-changing one. The far more dramatic difference is between the Delta wave and the previous winter peak, when 60,000 daily cases produced about 1,200 daily deaths. In the U.K., between that point and Delta, a tripling of daily cases produced one-tenth as many deaths. That is a 30-fold reduction, an effect 15 times the change observed with Omicron.

And if it is those reductions — before Delta, from vaccination — that have landed the U.K. and indeed much of Europe in a much better place now, it is concerning that we saw nothing like them, over the same time period, here in the U.S. Here, there was essentially no change at all in the ratio of cases to deaths between the pre-vaccine winter surge and the post-vaccine Delta wave. Last January, a case peak of 250,000 produced, ultimately, a death peak of about 3,400; with Delta, a case peak of about 160,000 produced a death peak of about 2,100. Just under two-thirds as many cases produced just under two-thirds as many deaths. It was as though, in the interim, the vaccination rollout hadn’t happened at all. Of course, we know that vaccines do work — study after study about the divergent outcomes of the vaccinated and unvaccinated show an enormous effect. But at the national level, the effect of mass vaccination was weirdly invisible, at least with Delta — the vaccines and that variant roughly fighting to a draw. In Europe, they observed the predicted effect of mass vaccination; here, with only somewhat lower rates, there was hardly any effect at all.