New York’s already taken his advice, by the way. The viewing area in Times Square for the ball drop this year will be scaled back from 58,000 to 15,000 to allow for distancing. Proof of vaccination is required. So are masks — even though it’s outdoors.

Top U.S. infectious disease expert Anthony Fauci said attending large gatherings of more than 40 people is considered not safe for vaccinated people, even those who got a booster dose https://t.co/FwFRsbXIfV pic.twitter.com/xJ9AHQhl8e

— Reuters (@Reuters) December 22, 2021

Is Fauci suggesting that the boosters don’t work? No, Fauci’s focused on community spread, not individual risk. Boosted people aren’t going to die if they attend a Christmas party but they can pick up the virus there and end up infecting someone who will.

In fact, new data from the UK shows that whatever protection from infection you get from them initially falls off pretty quickly afterward.

VACCINES

Speaking of boosters, it’s not great news I’m afraid.

Updated vaccine effectiveness analysis shows mRNA boosters beginning to wane from one month (week 5-9) for Omicron, and as low as 30-50% effective from 10 weeks post-booster.

This effect is not seen with Delta. pic.twitter.com/g0tLxH3vLR

— Meaghan Kall (@kallmemeg) December 23, 2021

The bottom graph is the relevant one. (The top one is for people who got AstraZeneca’s vaccine, which isn’t available in the U.S., for their first doses.) If you’ve had two shots of Pfizer and then get a third dose, your protection against infection by Omicron will drop to around 50 percent within just five to nine weeks afterward. If you mixed and matched and got Moderna as your booster instead, effectiveness between five and nine weeks remains at around 75 percent. That’s better, but you can see why Fauci’s imagining even boosted-only gatherings potentially turning into superspreader events.

To be clear, though, we’re talking about protection *from infection* here, not protection from severe illness, which should remain solid. That’s the counterargument to Fauci — if the worst boosted people have to fear is a few days of mild symptoms before recovering, why can’t they make the choice to party?

To which he’d reply, “What happens when the chain of transmission you started ends up in the local nursing home?”

Speaking of vaccines not working, our very good friends in Beijing suddenly find themselves in a pickle with the Olympics just six weeks away:

Two doses and a booster of the Covid-19 vaccine made by China’s Sinovac Biotech Ltd., one of the most widely used in the world, didn’t produce sufficient levels of neutralizing antibodies to protect against the omicron variant, a laboratory study found.

The research suggests that people who’ve received Sinovac’s shot, known as CoronaVac, should seek out a different vaccine for their booster: Getting Germany’s BioNTech SE’s messenger RNA as a third dose saw those previously fully vaccinated with CoronaVac significantly improve in protective levels of antibodies against omicron, according to the study from the University of Hong Kong and The Chinese University of Hong Kong.

Does China have a billion doses of Pfizer’s vaccine sitting on a shelf somewhere? It’s gonna need them.

The best-case scenario there, here, and everywhere else is that Omicron infects everyone, kills practically no one, and confers enough immunity against other variants that it operates essentially as a vaccine against more dangerous strains of COVID. A model from IHME foresees that the new variant will indeed be drastically less lethal to the population than Delta was:

Despite lower IHR, pressure on hospitals is likely to
be similar to last winter, IHME models, with considerable variation across states.

Infection-fatality rate (IFR) expected to be 97%–99% lower than for Delta. (2)

— Meg Tirrell (@megtirrell) December 23, 2021

What about the immunity part, though? Does catching Omicron protect you from Delta and vice versa? Some scientists are skeptical. New York magazine spoke with a British epidemiologist about a curious wrinkle in the data lately, the fact that so many people infected by Omicron turn out to have been vaccinated. It’s almost as if vaccination makes you more susceptible to the new variant than if you’re unvaccinated. Could that be? Nah, said the epidemiologist. The reason the Omicron numbers among the vaccinated seem so steep is because the Delta numbers among the vaccinated are much less so by comparison. For the moment we seem to have a two-track pandemic in which the mild variant that’s capable of puncturing immunity is spreading among the vaxxed while the more dangerous variant that’s less capable of puncturing it keeps looking for non-immune people to infect. Ideally if an unvaxxed person catches Omicron it’ll protect them from Delta, but that’s not a sure thing.

[Q.] And getting back to the simultaneous-wave hypothesis … If Delta is basically stable and Omicron is growing in a distinct immunological niche, what does that mean going forward? Will those people now getting Omicron have an immune advantage with Delta, or not? Is it possible this whole wave is going to wash over the population and confer no additional immunity at all on those getting these Omicron infections? For a while, it seemed likely that a breakthrough infection offered a real advantage going forward, but that requires robust cross-protection from one strain to the next.

[A.] This takes us into the realm of conjecture, but I’ll tell you what we know so far. We know that previous infection from previous variants offers only about 20 percent protection from Omicron infection. That is down from 80 percent protection before, with the earlier variants, to 20 percent, with this one. The cross-protection is not zero, but it appears massively reduced. And given that the antigen is so different and people who were infected with previous variants have a much lower level of protection against Omicron, I would think that the opposite would be true as well, although I haven’t seen any reports about it. I think that’s an open question, but I think it is entirely plausible that Omicron immunity will not protect to the same extent against Delta as infections from earlier variants have.

[Q.] Which could mean that the whole wave may not mean all that much for overall immune protection in the population.

[A.] If that is the case, then the real worry is that you might get infected with one variant, not develop immunity to the other, and then still be susceptible to another variant that is circulating at high levels in the population. It’s kind of like two different pandemics in a sense. They have a little bit of cross-protection, but not a lot.

If one variant isn’t generating (much) immunity against the other, that means Delta will keep spreading and killing the unvaccinated, including some unvaccinated who’ve had Omicron. We shouldn’t see deaths skyrocket this winter overall but we also shouldn’t see them decline, as we’d expect if a mild variant were able to suddenly replace a more dangerous one across the population. It looks like the two strains might co-exist. Not the best-case scenario.