We’ve had even more data come in this week on Omicron.

I want to highly recommend two recent excellent essays on all this.

The first one is about the “is it mild or not” question. The piece will not be a surprise to anyone who read the favorite of this newsletter, Novelty Means Severity, by Dylan H. Morris.

Still, I found it really useful for explaining to people what it means for a virus to be experienced as milder over time. It’s by Andrew Pekosz, published in the New York Times.

Will Covid-19 become milder over time? The answer to that question is most likely yes, but it may not have anything to do with the virus evolving to induce milder disease.

Scientists now know that SARS-CoV-2 can, at least to some degree, reinfect people who were previously infected or vaccinated. The combination of prior infections and vaccinations are building immunity in the population. This immunity isn’t perfect because it can’t block infection completely, but it does dampen the disease the virus can induce by shortening the time of infection, reducing the amount of virus that is produced and therefore reducing the symptoms and disease….

In December 2019, SARS-CoV-2 entered a human population that had no immunity to it. In December 2021, the Omicron variant is entering a human population that has a large amount of immunity to SARS-CoV-2. That immunity in and of itself will lessen the disease severity of the variant. But in people with limited or compromised immunity, such as the unvaccinated, the elderly or the immune compromised, SARS-CoV-2 may still be able to cause severe disease because they don’t have protection conferred by pre-existing immunity.

The second essay I’d like to really recommend is by the excellent duo Jesse Bloom and Sarah Cobey, on what we know, how, and what else we need to wait for, also in the New York Times. They answer many key questions on this, including what mildness/severity means in this particular case, and how we can try to figure it out.

Will the immunity we have still protect us against severe disease?

Even if some antibodies fail to block infection by Omicron, T cells and other antibodies developed from vaccination or infection may provide some protection against severe illness. In other words, deaths and hospitalizations may not track cases as closely as they have in previous pandemic waves. Measuring this requires data from clinics, hospitals and epidemiological studies that follow infections and symptoms in people over time. Such studies take more time than experiments in a lab.

It typically takes several weeks for severe Covid-19 to develop, which is why deaths and hospitalizations are what scientists call a “lagging indicator.” So while it’s fine to be optimistic when we hear early anecdotal reports about vaccinated people having only mild symptoms, remember that it will take time to have reliable data on disease severity overall. For example, it’s possible that Omicron could cause milder disease in people who have been previously vaccinated or infected but cause severe disease in people with no immunity. This will have implications for the burden that might be placed on hospitals.

In sum, for me it comes down to this:

zeynep tufekci @zeynep

So essentially, "most vaccinated/infected people will experience a milder course" can be true without the virus being intrinsically milder, and the threat can change with age, immunocompetence and virus evolution. This is fairly mundane, by the way.

2:42 PM ∙ Dec 10, 2021

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What is off the table? I think it is increasingly unlikely that this variant is also significantly severity-escape, not just antibody-escape. We knew almost immediately that it could cause breakthrough infections and re-infections, but clinically speaking, we’re just not seeing what we saw in Spring of 2020 when nobody had any immunity to it.

The picture for the elderly remains open, but again, they need the booster against Delta as well, so the recommendation is the same for them: get the booster ASAP. For the world, it means that we need to booster the global population, starting with the most vulnerable everywhere.

However, even in the best case scenarios, a large number of people getting mild illnesses all over a few months, with a small fraction having worse outcomes can be a huge deal if for no other reason than hospital stress! A small percent of a very large number is a large number!

zeynep tufekci @zeynep

Also: even if Omicron cases in vaccinated/infected people are overwhelmingly mild🤞but symptomatic, a huge wave can still be a strain. If a tiny percent of those are severe that can add up quickly if the wave is big enough. Remember it is in *addition* to other seasonal viruses.

6:40 PM ∙ Dec 10, 2021

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A booster seems to restore a lot of the infection-fighting ability, and a combination of being infected and vaccinated seems to be really strong as protection: having seen multiple versions of the virus (the vaccines are still going off the ancestral Wuhan spike that is nowhere anymore with all these variants), the immune system is much better at fighting it off.

What Omicron will it mean for the completely immunologically naive remains unknown, but whatever the answer, Delta is ready to stalk them anyway, so I’m not sure if the answer matters that much.

For people traveling: I think the advice remains the same. Especially for the elderly, boosters at least two weeks ahead of time are essential. The rest is the same: good masks like N95s, rapid tests before gatherings, ventilation/air-filtering and… be prepared to be stuck somewhere if crossing borders because the odds of testing positive despite vaccination or prior infection have gone way up.

But overall, I increasingly notice that doctors and scientists in South Africa are less worried about it compared to when all this broke, and I think what data we have supports that conclusion: cautious optimism while still preparing for a wide range of scenarios simply because an ounce of prevention is worth a pound of too-late-action. Optimism isn’t a policy by itself, and a wide range possibilities absolutely remain on the table, and there just has not been enough time and different populations to figure things out conclusively.

But let me end by a tweet by one of the first scientists to alert the world to all this, to think of South Africa not just by the amazing science and responsible, exemplary behavior we have lately seen, but also this: beauty.

Tulio de Oliveira @Tuliodna

I traveled to > 100 countries. Amazing places and amazing people. But I have not seen diversity and nature like South Africa. Maybe bias to have been happy here, maybe due to two oceans (Indic and Atlantic), maybe ecosystem & biodiversity. It should be on everyone's buck list...

3:20 PM ∙ Dec 12, 2021

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