A decent summary of the likely causes of our declines. A few comments:
This isn't a Biden thing. Case reports peaked around Jan 10-12, which would indicate that infections peaked around Jan 4 or so. That's consistent with a post-holiday decline, but not anything the Jan 20 inauguration could change. Even if Biden waved a magic want on Jan 20 to instantly slow the spread, it wouldn't show up until around Jan 30, by which time cases were down 40% from the peak. Still, good to see sane leadership and the much more active CDC since then.
This mostly isn't a vaccine thing...but that's changing. The numbers were too small back in early January to make a big difference. But we're adding 10 million people a week to the immune category, and that's going to progressively squeeze transmission just as B.1.1.7 is boosting it.
(By the way, we're around 8% B.1.1.7 now, it should reach 50% in late March and dominance in April. That may end our decline or even start a short-lived increase.)
Of the arguments in the article, I find the seasonality one to be very weak. We saw how COVID can spread in March/April in northern Italy and New York City, it's not a "January's here, COVID season is over" thing. In Europe, their big wave started with a consistent increase from August onward, it would be equally silly to attribute most of this to the end of winter.
I think the two big issues are behavior and immunity. Now that the expanded social networks of the holidays are behind us, people are less exposed, and reports suggest that masking is both more prevalent and more proficient now that we've had a few months to figure it out. Immunity is big enough to make a difference, roughly 1/4 of the people in the US have already had COVID, which by itself is enough to drop Rt from 1.2 to 0.9. (Actually more than that, because the most-exposed people are over-represented in the immune category now.) And even accounting for overlap, that's about 35% with vaccinations added in, giving us a bit of a tailwind.
While B.1.1.7 has a chance of giving us another wave of cases in April, I'm fairly confident that our hospitalization and death numbers are in permanent decline, because we're vaccinating so many of the vulnerable people.
