The short answer, I guess, is “because the CDC said so.” The new guidelines issued a few days ago recommended masks for everyone, vaccinated or not, in all indoor public spaces. Biden, Harris, Pelosi, and members of Congress weren’t about to flout the new rules before a national audience.

But wait. Do the rules forbid unmasking in a public space where everyone is vaccinated? Recall that the CDC has already signed off on vaccinated people from different households holding small indoor gatherings without masks, so low is the risk of infection between them. The new guidance about masking up in public spaces like restaurants is aimed at situations where you have a crowd of strangers and no one knows who’s been immunized and who hasn’t. In that situation, says the CDC, err on the side of caution.

That wasn’t the situation in the Capitol last night. The vaccination status of everyone who attended could have been checked beforehand and the rules relaxed accordingly. The fact that that didn’t happen made it a missed opportunity to show Americans the power of vaccines, argues Dr. Leana Wen:

Look, I can understand the need for caution with our nation’s top lawmakers. Many are older and could be at high risk for severe disease if they contract covid-19. But with a breakthrough rate of 0.008 percent, there is most likely no one who has coronavirus in a room of 1,600 vaccinated people. An additional precaution could have been testing for all attendees, which would reduce the risk of an asymptomatic carrier to effectively zero. Another benefit of the vaccines is that they reduce the likelihood of severe illness, so even if someone were to become infected, almost certainly they’d have mild symptoms that would not result in hospitalization.

Surely, those are odds our leaders should be willing to take on to demonstrate the benefit of vaccination to the American people.

Perhaps Biden wanted to differentiate himself from his predecessor. To be sure, it was horrific to see President Donald Trump’s many maskless, packed superspreader events in the midst of the worst of the coronavirus surge. But the message coming from Biden isn’t right either. Over-correction has a price; at best, it makes public health measures seem performative rather than science-based. At worst, it calls vaccine efficacy into question.

I think Biden and Pelosi stuck with masks for two reasons, neither of which had to do with the safety of those in the chamber. One was the perpetual fear that, if vaccinated people let down their guard, unvaccinated people will take a cue from them and do the same. “[J]ust like we can’t tell only the sick to wear masks,” writes Zeynep Tufekci, “we cannot tell only the vaccinated to chuck their masks indoors—a grocery-store clerk shouldn’t have to police this. For now, indoor spaces have to keep masks as a rule simply for sociological reasons.” That’s why they kept them last night, I assume, for the “sociological” reason of signaling that masks are good practice indoors as a rule until we’ve reached a higher degree of herd immunity.

The other reason, identified by Wen herself, is that if the sergeant-at-arms had started checking the vaccination status of attendees, he might have discovered that some member of Congress on the premises hadn’t had their shots yet. And if so, he and Pelosi would have been forced to decide whether to bar that member from the chamber for the evening. (Lauren Boebert, a strident MAGA populist, was there. I don’t know whether she’s been vaccinated but she comes from one of the most vax-resistant demographics in the country.) That would have embroiled Biden and the Dems in a controversy over whether they were requiring de facto “vaccine passports” for the evening, a subject which the White House has been eager to avoid. If a noisy Trumpist like Boebert had been barred on grounds that she hasn’t been immunized, righty media would be awash today in indignation and warnings that the White House was embracing passports after claiming it wasn’t. Biden and Pelosi probably calculated that that would be an unwelcome distraction on a day when they want the coverage to be about Biden’s speech so they decided to admit all comers and simply ask for masks to be worn.

Anyway, Wen is thinking about how to incentivize holdouts to get vaccinated. Show ’em that even a crowd of vaxxed rich senior citizens can gather safely without masks and that’ll communicate in a powerful way just how effective the vaccines are — in theory. In practice, I’m skeptical that holdouts are holding out because they’re still not convinced that the vaccines work as well as everyone says and need a visual demonstration. Most, I suspect, are wary because they fear as-yet-unknown long-term side effects from the vaccine or believe that the threat from COVID itself is overstated. If you want to incentivize those people, you need more than a tableau of what they can do socially once they’re immunized, because guess what? Plenty of unvaxxed people are already socializing without masks, regardless of what the CDC says.

Back in early March I offered this idea for how to get the fencesitters motivated:

Since we know the percentages of each state’s population that have received their first and second doses, why not tie restrictions like capacity levels for businesses and the status of the mask mandate to vaccination benchmarks? For instance, once 25 percent have gotten both shots, businesses statewide are authorized to open at 50 percent capacity no matter what their local authorities say. At 40 percent vaccinated, businesses move to 75 percent capacity. At 60 percent, all capacity limits lift and the mask mandate is canceled.

Lo and behold:

A really innovative, smart strategy by @GovWhitmer to tie loosening of public health restrictions to vaccination rates in Michigan

Because metrics like infection #s fluctuate

But immunity through vaccinations is more durable

And lets hope this motivates folks to get the shot pic.twitter.com/6om3qN2mop

— Ashish K. Jha, MD, MPH (@ashishkjha) April 29, 2021

The hitch is that business owners are destined to get antsy about the slow pace of reopening if Michiganders don’t scramble and start lining up for vaccinations immediately. If you own a bar or a gym, why should your capacity limits hinge on whether tens of thousands of people living out in the sticks, who’ll never visit your establishment, ultimately decide that they’re willing to risk having a Bill Gates microchip inside them by opting to get vaccinated after all? Maybe Whitmer can tweak the benchmarks so that the vax thresholds are measured by city or county uptake rather than statewide.

I’ll leave you with Wen making her case this morning on CNN.

.@DrLeanaWen: We should tell Americans their “moment of freedom” will come “when you get vaccinated” pic.twitter.com/LBzQezYVF4

— Tom Elliott (@tomselliott) April 29, 2021