Why is it winning and how do we need to change our tactics?

Welcome to Plugging the Gap (my email newsletter about Covid-19 and its economics). In case you don’t know me, I’m an economist and professor at the University of Toronto. I have written lots of books including, most recently, on Covid-19. You can follow me on Twitter (@joshgans) or subscribe to this email newsletter here.

B.1.1.7 is the scientific name for the SARS-CoV-2 variant that is now spreading across the globe due to it being 50 percent more transmissible than all the other SARS-CoV-2 variants. Some in the media have tried to relabel it as the ‘UK Variant,’ ‘Supercovid’ or ‘Covid 2.0.’ Some scientists are arguing whether it should be considered a new strain rather than a variant. All this is saying that it is not good news. But I kind of think that ‘B.1.1.7’ is a good name. It is not intrinsically scary unless you are “in the know” in which case you can explain to other how bad it is and get that extra jolt of fearful emotion every time you see B.1.1.7. After today's post that is going to happen to all of you if it hasn’t happened already.

A few things first about B.1.1.7. Apparently, most of its mutations (and there is a couple of dozen) involve mutations to the spike protein that allows the coronavirus to latch on and take over cells. This is also the target of many vaccines and so there was concern our vaccines may not be adequate. The evidence thus far looks promising that we are OK on that front although, as I will explain below, vaccines are an issue because we are distributing them widely and they aren’t particularly diverse — in particular, the mRNA vaccines do kind of the same thing so the virus mutating around them is far from off the cards. Here is Michael Mina from Emily Oster’s substack who explains it nicely.

Importantly, it is possible that this virus could mutate at any moment. And it could mutate around the vaccine derived immunity. All of the leading vaccines are narrow scope single protein vaccines. Unfortunately, all four of the leading vaccines for use in the US are essentially identical – so not only are the vaccines themselves narrow in scope, but the entire vaccine program, the whole basket of vaccines is narrow in scope. That means we need just a single virus particle, somewhere out there in the world to learn how to evade the narrow single protein derived immunity of the vaccine to render the vaccines potentially useless or at least much less powerful. This should have been a major consideration long ago but it wasn’t and still is barely a talking point. No one wants to talk about this real risk. 

Similarly, B.1.1.7 does not seem to involve greater health harm than other SARS-CoV-2 variants which means that any risk to our health system is coming from more transmission rather than from more virulence. That said, while that might feel comforting, it is not. Transmission is the bigger enemy here. Recent data from the UK, who have a much wider genomic testing infrastructure than other places, shows for quickly B.1.1.7 has taken over.

Lest you think it is just a change in shares. Here is some data on the numbers of cases.

The take-a-way from this is that sometime in late November, B.1.1.7 started to ‘win.’ It is not just brand new. It is pushing other variants out. As I will explain below, this tells us more about this variant than just that it is more “transmissible.” And that has implications for how we deal with it.

The evolutionary contest

Back in the day, I dabbled in evolutionary game theory. (Look it was the early 1990s ok, I was just a graduate student and all our moral compasses had been ravaged by the 80s and besides the person how invented evolutionary game theory was John Maynard Smith. Think of it. John.Maynard.Smith. A perfect amalgam of the most impactful economists Adam Smith and John Maynard Keynes! How was a young economist supposed to resist????).

Anyhoo. What evolutionary game theory allows us to do is forget, for a moment, the obvious fact that a virus and its mutant offspring are not conscious strategisers but consider them “as if” they are. Because even without thought, the fact that mutations are selected on the basis of evolutionary fitness is enough to make them do the things that someone who was trying to optimise their survival might do. (Here is my old paper proving just that).

Scientists have claimed that B.1.1.7 will become globally dominant. But near as I can tell, this is just based on different exponential growth rates rather than why that is the case. Herein lies the puzzle. The biggest competitor for B.1.1.7 is not us or something like it but the other SARS-CoV-2 variants. They were doing quite well until B.1.1.7 came along and then it managed to take over. But if it was just more transmissible, in the sense of having higher viral loads (as seems to be the case), then what we would see is that more of the new case growth would be attributable to B.1.1.7 but that the other variants would likely be able to continue to just fine. After all, prevalence is still low enough that every variant can surely find people to infect.

Instead, the new and old variants are fighting over people to infect. And B.1.1.7 is winning. In other words, B.1.1.7 is starving the old variant for hosts. That is surprising as the older variants had a head start. Older variants were more prevalent and so, other things being equal, had a higher potential for growth. You might expect pockets where the new variant does well but not all over and not on the seemingly the same turf as the older variants. In other words, B.1.1.7 is winning in a head-to-head contest with older variants. This is not simply a race but a fight. We need, therefore, to ask why B.1.1.7 is able to win this fight? And, indeed, what fight is it winning? What is its unfair advantage over old variants?

Here is where that thought leads me. And I want to stress at this moment, I am, once again, not an epidemiologist, and so there may be reasons why what follows is off-base. But let me tell you how it looks to this game theorist.

Before B.1.1.7 the SARS-CoV-2 variants were born on the properties of the originating novel coronavirus. This is the one that was able to spread quickly because it caught us unawares. We didn’t know what it was, how it spread, when symptoms occurred, how it related to infectiousness, whether it could be on surfaces, how well masks might work and what sort of social contexts it could spread in. We eventually answered those questions and adjusted our behaviour. In places where the virus is still prevalent, we cut its reproduction number from about 2.5 to around 1. This was largely by avoiding indoor gatherings and when they couldn’t be avoided wearing masks. This was enough to reduce super-spreader events but also keep transmission following those events at a lower ebb. This gave us a calmer summer that extended into fall in the Northern hemisphere. Coincident with the rise of B.1.1.7 all hell has broken through this past few months.

Here lies the point: our current mitigation actions were reasonably effective in reducing the reproduction of the coronavirus. That virus mutated but it wasn’t until it mutated in a certain way that B.1.1.7 was able to get through. Thus, a person who was exposed with mitigations to older variants would now be caught by B.1.1.7. This is how it wins the fight. B.1.1.7 has an advantage over older variants in infecting people when the mitigation strategies are in place. In other words, it is getting around them.

I think of this because every news report on B.1.1.7 ends like this one:

Until more is known about the B.1.1.7 variant, Barrett said current public health measures including physical distancing, wearing face coverings and frequent hand washing need to be maintained to help limit its further possible spread.

"The best way of doing this is making sure that we don't have a lot more cases, limit travel, hand wash, distance, mask -- we've got to stay at it for a while longer," Barrett said.

It is hard to object to the advice, do more of the same and with more vigilance. But we do need to understand if that is enough. Evolutionary game theory tells us that it is the wrong place to be pushing in our fight.

My guess is that the new variant can obtain more cases in certain settings — like workplaces that previously were able to keep transmission low — and then people carry the new variant home where fewer mitigations are in place and transmission occurs more easily there. Indeed, in Ontario, 50% of new cases are within household transmission at the moment. Under current practices, it is likely that it is being brought more often into households where it spreads quickly. In other words, the path from work to home is stronger.

That means that the fight against B.1.1.7 requires the places that have been the most vigilant need more action. It is hard to know what that is. One option is to shut them down but those workplaces are open for a reason. The other option — and I will continue to beat this still live horse here — is ramping up testing. We need those workplaces to have regular screening for Covid-19. We need it now more than ever. Again, here is Michael Mina:

These tests will be “immune” to such changes in the virus and can induce herd effects through empowering people to know their status and thus help people to not transmit the virus to their loved ones. If enough people do this, R can fall below 1 and the virus can diminish at the community level, like we saw in Slovakia. In other words, these tests can stand in for vaccines during the rollout, or in the catastrophic case that the virus mutates and evades the vaccine derived immunity.

Rolling out the vaccine is one thing but ramping up screening in the right places is another distinct thing. B.1.1.7 tells us we need to do that now. Otherwise, we will have too many infections and too many hospitalisations and frankly, we won’t need the vaccine anymore.

What did I miss?