Benjamin McMichael

I recently filmed a three-hour podcast with Jake Glanville, the CEO of @centivax, and the episode should come out soon. But he said so many surprising things that I had to investigate afterward. At one point, he argued that we could eradicate the flu entirely. Like, if we had a vaccine that was broadly protective against many different strains and 90–95 percent effective at preventing infection, say, then we could plausibly vaccinate enough people that flu stops circulating in humans. You’d also have to vaccinate animals, including pigs and birds, which might make this much harder. But Glanville said he thinks this is feasible partly because, during COVID, we eliminated an entire lineage of influenza. Very few people seem to know about this. I certainly didn’t. There was a lineage called B/Yamagata that had been circulating since the 1970s. As recently as 2018, it accounted for about 90 percent of influenza B infections that we've sampled. But the last confirmed case of a Yamagata infection was in Arizona in March 2020. We haven’t seen any naturally circulating Yamagata since, and it's been six years! There are a few ideas about how this might have happened. 1. Yamagata has no known permanent animal reservoir to replenish it (it just spreads between humans) so the normal COVID precautions may have stopped its normal transmission. 2. It was already in decline after a big 2017–2018 epidemic, when it infected lots of people and caused them to develop antibodies. And since the Yamagata line mutates relatively slowly, it needs a longer time to "escape" those antibodies already present in the human population. We can’t say for sure that it’s gone, but recent flu vaccines have *not* included this line. And it seems to suggest that population immunity + lower mutation (perhaps via immunization of animal reservoirs) really could plausibly be used to eradicate influenzas. This is obviously speculative, in part, but I thought interesting enough to share.