It’s right here, halfway down a long jargon-y page about vaccine administration. We’re nearly a year into the pandemic and I doubt more than five percent of the population could cite any CDC instructions beyond the most basic stuff like “wear a mask” and “stay six feet away.” The new rule exempting certain people from quarantine turns out to be a three-part test, and needless to say, hardly anyone will be rigorously applying that test in deciding whether to break quarantine or not.

However, vaccinated persons with an exposure to someone with suspected or confirmed COVID-19 are not required to quarantine if they meet all of the following criteria†:

* Are fully vaccinated (i.e., ≥2 weeks following receipt of the second dose in a 2-dose series, or ≥2 weeks following receipt of one dose of a single-dose vaccine)

* Are within 3 months following receipt of the last dose in the series

* Have remained asymptomatic since the current COVID-19 exposure

That’s the official rule. The actual rule that’ll be followed by most of the public is “if you’ve been vaccinated then you don’t need to quarantine, period,” in much the same way that the informal rule on mask-wearing is “if you’ve had the disease and recovered then you don’t need to mask up.” (Ask Rand Paul.) The caveat about three months popped out when I first read this because it suggests that immunity from vaccination could be short-lasting, which is news to me. Last I checked, Moderna was boasting that they expect immunity from their vaccine to last a year or more. Which means the CDC’s timeframe is probably an abundance-of-caution thing, i.e. “we’re confident that immunity will last three months and soon hope to confirm that it’ll last longer, but until we do, play it safe.”

To the extent that people do hear about this new guidance, then, I wonder if the big takeaway will be, “Wait, the shot only protects you for three months? Screw it, then.”

You’re probably asking yourself, “If we’re not sure yet whether vaccinated people can still contract the virus and pass it along to others, why would we tell them that they don’t need to quarantine after exposure?” The answer, per a doctor at Brown University, is that we *are* pretty sure that vaccinated people won’t spread it — at least if their case is mild enough as to be asymptomatic, which explains why the CDC made that a part of the three-prong test too:

1) New preprint from Israel (not yet peer-reviewed, and small dataset):

A 4-fold decrease in viral load among those who happen to have a breakthrough infection, among those who have been vaccinated.

SO PROMISING – bc viral load <-> infectiousnesshttps://t.co/T2hXcfewAm pic.twitter.com/ZtqgG6Fh5Q

— Megan Ranney MD MPH 🗽 (@meganranney) February 11, 2021

She went on to note that data from both the Moderna and Oxford vaccine trials also supports the belief that vaccinated people are less likely to transmit the virus, not just less likely to get sick themselves. Still, it seems like there’s *some* small risk of transmission and yet the CDC is encouraging vaccinated people to skip quarantine and expose the people around them to that small risk. How come?

I assume they’re worried about “vaccine hesitancy” among the public. The CDC’s taken heat from the commentariat lately for “underselling the vaccine” by giving the public no concrete incentives to get the shot besides the obvious one. We’ll all need to wear masks for months after being immunized, Fauci has said, in order to prevent unvaccinated people from getting infected. We’ll also need to keep up social distancing to some greater or lesser degree well into fall as well, to hedge against the spread of the new variants. If life’s going to carry on more or less the same whether you’ve been vaccinated or not, why would a vaccine-skeptic take the plunge?

Today’s new guidance may be a small gesture towards incentivizing that group. If you get the jab and someone in your household comes down with COVID, you’ll no longer be expected to remain housebound for two weeks. They’re sweetening the pot, promising a little extra science-sanctioned freedom for those who do the conscientious thing. After all, although we have a supply problem with our vaccination effort at the moment, that’s going to shift to a demand problem within the next month or two. The White House announced just within the past hour that it’s ordered another 100 million doses each from Pfizer and Moderna, which means the U.S. will eventually have enough of a supply to vaccinate 300 million people. As distribution bottlenecks ease and more doses roll out this month and in March, the main challenge for authorities won’t be delivering the vaccine to people who are waiting for it, it’ll be convincing people who are iffy about it to go get it now that it’s readily available. The new guidance is a nod to that. No more quarantine if you’ve been vaccinated! (For three months afterward, provided that you have no symptoms.)

Here’s Fauci this morning sounding optimistic about the supply come April. That’s when we should finally reach “come and get it” mode for the general public.

“By the time we get to April, that will be what I would call open season,” Dr. Anthony Fauci says about the timeline for vaccination availability for all groups to begin getting shots. pic.twitter.com/BMGD3YSVex

— TODAY (@TODAYshow) February 11, 2021