Brief bonus COVID update

Don't believe the hype

I stopped with the regular weekly COVID updates four weeks ago, because it felt like there wasn’t enough data to justify it (with the removal of ONS and regular sequencing data through COG-UK). On the other hand, the problem is that this creates an information vacuum, which isn’t helpful either, so here’s a quick update.

There have been alarmist rumblings about the latest variant, XBB.1.16. The usual suspects have decided to name this Arcturus, having previously been on the Kraken hype train (“deadliest wave in pandemic history”) around the beginning of the year.

So you might see headlines like this

New Covid variant ‘Arcturus’ is even more infectious than Kraken and could push UK cases higher

But fundamentally, this needs putting in some kind of context. The figure of “nearly 1.2 times as transmissible” sounds scary, but it’s worth bearing in mind that this is presumably a “per generation” advantage, and probably compatible with the 6-7% daily advantage estimated by Alex here:

In the context of previous waves, this size of advantage is not huge. A handy rule of thumb (developed by Alex) is that the size of the wave will be proportional to the square of the advantage. This equates to a wave about a quarter of the last big one - the BA.5 one of early last summer, which had something like a 14% daily advantage as plotted here.

Further, as the article itself says, there is no evidence that this new variant has greater severity - and for all the talk of new symptoms associated with it, they don’t necessarily seem of themselves to be that alarming, compared with previous waves which threatened healthcare capacity with huge demand from the older members of an unvaccinated population.

Finally, it’s worth remembering that for all the headlines, this variant is currently at a low share in the UK. Of course, if the growth advantage persists, then that will change and it will ultimately displace XBB.1.5, but one variant taking over from another isn’t intrinsically bad news, particularly when the severity is similar.

And all of this conversation needs to happen in a context where admissions are falling towards their recent lows (albeit with a few swerves in the trajectory that might have been caused by Easter or changes in measurement standards)

And the ZOE measure that was the cause of the last excitement from inews continues to trend resolutely downwards over the last month.

In other words, the 6-7% growth advantage of XBB.1.16 can be somewhat discounted by being an advantage relative to a strain that is currently falling in absolute value (we are comparing the speed of the up and down escalator).

In short, I think that XBB.1.16 will cause a relatively small wave compared to last summer. It won’t be nothing, and if you are vulnerable enough to be offered a spring booster then it’s worth taking it. But it feels very much like the latest in a series of ripples, rather than a catastrophic wave like Alpha in the UK or Delta in India back in 2021.