How to read a variant article

I end up in crisis (tale as old as time)

Now that alarmist articles about COVID variants have become endemic, here are some things to look out for when reading them:

1. “Experts are worried”. Ok, but which experts? It’s pretty much a truism that there’s no opinion so silly that you can’t find at least two people with a PhD to endorse it. So when headlines talk in generic terms about “scientists worrying”, it’s always good to drill down into that. It’s fair to say that some people have a pre-disposition to worry, and others are more chilled: is the story just quoting the same names that have a tendency to crop up every time? For example the “Centaurus” (ugh!) variant in the headline above triggered a certain number of stories last summer and had almost no direct effect in the UK. One more thing to remember is that not all experts have the same expertise: it’s worth checking whether the person in question is a virologist, an immunologist or an epidemiologist (or something else), because those are different specialisms that come with different perspectives.

2. “This is the fastest-growing variant so far”. This is kind of taken for granted: if something is growing in share, it’s outcompeting what is there at the moment. But crucially, you can’t just keep multiplying R numbers by successive growth advantages to come out with wacky claims of R0 of 18 or higher. The size of any future wave is roughly determined by the growth advantage over whatever the dominant strain is now: any past evolution is already priced into the picture. So the key thing is to get some kind of reliable estimate of the rate of growth in absolute numbers, and to calibrate it against recent omicron waves.

3. “This variant demonstrates immune evasion”. Again, this is more or less the table stakes these days. By summer 2023, three years of waves and 145 million jabs since this thing started, there are a tiny number of people in the UK who haven’t had either at least one infection or injection. Successive rounds of boosters have been targetted at the most vulnerable and where waning is most likely to happen. As a result, antibody levels are very high across the population. If any COVID strain at all is going to spread, it’s going to have to have something up its sleeve to beat that high existing level of immunity. The key question is how much immune evasion it’s got - and that’s roughly captured already by the growth advantage mentioned above.

4. “Numbers have risen [Y%] in the last week in [Country X]”. Ok, but there’s a lot of countries and each one has data that’s subject to a certain degree of random fluctuation and uncertainty, so picking the place where the numbers have risen the most is unlikely to give an accurate prognosis for the UK. It’s much better to take some kind of weighted average across countries (as various good people do). But even then, it’s worth remembering that the average growth rate may not carry over between countries: most countries have now had slightly different sequences of waves, and different timings, eligibility and type of vaccines used for first injections and boosters. Ideally, you want to get an estimate of growth advantage just for the country you care about.

5. “The new strain has grown from 1% to 2% in the last week”. Sounds alarming! If we’ve learned anything from the pandemic, we’ve learned that exponential growth is bad. But it’s worth remembering that early estimates of growth rate can be very noisy (because so few cases are sequenced these days, so we can be talking about the difference between 1 and 2 cases of a variant seen per day) and often don’t continue to hold for a long time. Further, even if a strain is itself growing, it will only have a noticeable effect on the overall growth rate of admissions when it has reached a sufficiently large market share - perhaps 20% of cases or more - so there’s no point in worrying too much too early.

6. “This is a reminder that COVID continues to evolve and has not gone away.” Yup, it’s annoyingly good at that, isn’t it? Score one for Charles Darwin! But since delta arrived two years ago it’s seemed fairly clear that (at least with the first generation of vaccines) we were looking at a “slowing down” and a “learning to live with it” rather than a sudden full stop due to herd immunity, however nice that would have been.

7. “While this variant may not be too serious, it’s a warning that the next variant might be a bad one.” Again, of course. Who knows what might happen next week, or maybe already happened already but we didn’t spot it yet? But honestly, I’m with this piece:

   The idea, I guess, is that if and when disaster strikes, the person who rode out this period on misery cruise control now gets the satisfaction of never having gotten his hopes up. The less you expect, the more you'll be pleased, and all that. But man, what a bleak way to live — and for what? Whatever we do, the virus will do something unpredictable that results in a sudden resurgence of infections, or it won't. The nature of things is such that we won't know what's happening until it has already happened. 

   And I think the key thing to understand is this: all new variants start at 1 case. If we do suddenly jump into a completely new family of dangerous variants (call it pi) like the usual suspects keep telling us we are about to, then a higher level of omicron prevailing at the time would not cause faster evolution of that. (In fact, unless you believe there would be no immunity at all from omicron to pi, then having had more recent omicron is likely to slow it down - not that there aren’t other ways to do this). Of course higher levels of omicron give the virus more chances to mutate, but now we are up to many billions of infections worldwide and three really consequential jumps (alpha, delta, omicron - some of which may have happened in unusual patients with very long-term infections), it’s worth keeping a realistic view of the odds.

Of course, none of this to say is that variants won’t continue to cause COVID waves of some size for the next few years. As always, I would say that if you are offered a booster then I would be inclined to take it. But equally it’s worth trying to separate out the signal from the noise, and work out which variants are more serious than others, and the current media coverage doesn’t always make that easy.