If not for Biden’s federal vaccine mandate, this decision would be largely academic for red states, right?

CDC Director Rochelle Walensky on boosters: "We have not yet changed the definition of fully vaccinated … We may need to update our definition of fully vaccinated in the future." pic.twitter.com/PTfcZLfY81

— The Post Millennial (@TPostMillennial) October 22, 2021

The CDC declaring that you’re not fully vaccinated until you’ve had three doses would mean that vaccine passports and employer vaccine mandates for workers would now require an extra shot. But those policies are being used widely only in blue states as far as I’m aware. There are some individual businesses in red states that require employees to get vaxxed but (a) they’re free to decide for themselves what “fully vaccinated” means and (b) a worker who doesn’t want to comply with their boss’s mandate can seek work somewhere else.

In Texas, Greg Abbott has banned businesses from requiring vaccine passports and from mandating vaccines for staff. If those rules stand up in court, it wouldn’t matter to Texans what the CDC says.

The federal mandate complicates that, though. Because it applies to all businesses with 100 or more employees, even large employers in red states, it lets the feds dictate to those businesses what constitutes being “fully vaccinated.” And it limits an unvaxxed worker’s options if they want to switch jobs since all large businesses will be forced to follow the same federal rules.

If the Supreme Court upholds Biden’s mandate, which is doubtful, the CDC’s new definition of “fully vaccinated” would suddenly matter intimately to many millions of Americans.

But they can’t issue that definition yet. At the moment, boosters for Pfizer and Moderna recipients are limited to all senior citizens plus those aged 18-64 if they’re at special risk due to their health or the nature of their job. As such, unless and until boosters are recommended for all adults, the definition of “fully vaccinated” would vary from one demographic group to another. Are you 64 and healthy? Then you’re fully vaccinated with two shots. Are you 65? Three shots, then. Are you 40? You’re fully vaccinated with two shots if you’re healthy and three if you aren’t. Further complicating matters is the fact that Johnson & Johnson recipients have fewer antibodies over time than those who got the mRNA vaccines have and therefore all adults 18 and over who got J&J are eligible for a booster right now. So if you got the, ahem, “one-dose vaccine” and haven’t had a second dose of it yet, you might not be “fully vaccinated” under a new CDC definition.

There have been rumblings over the past few days that the agency is about to expand eligibility for boosters. Maybe not to all adults but certainly to the middle-aged:

Booster protection could soon expand to a much broader population, as a source says the US government likely will soon recommend additional doses to people as young as 40 who received a Moderna or Pfizer Covid-19 vaccine.

“I believe it will happen,” the source familiar with the plan told CNN’s Elizabeth Cohen. There is “growing concern within the FDA” that US data is beginning to show more hospitalizations among people under age 65 who have been fully vaccinated, the source said…

The FDA would consider lowering the age range on its emergency use authorizations for booster shots once more safety data comes in, officials told reporters on Wednesday.

“It’s a matter of having the data,” said Dr. Peter Marks, director of the FDA’s vaccine arm. “We want to make sure that if we deploy the boosters in all of the age ranges, that we truly are making a benefit outweigh any risk.”

We’d still have a two-tier regime of what constitutes “fully vaccinated” if the CDC expands eligibility. Forty and older means you need three shots, 39 and under means you need two. But that’s easier to administer than the hash I described above. Plus, I’m guessing that most Americans who got two shots won’t be opposed to getting a third, particularly senior citizens in light of their vulnerability to COVID. In a world without mandates, changing the definition of “fully vaccinated” probably ends up not mattering to most people.

In a world where there’s a single federal mandate that’s upheld by the Supreme Court, it’s a big deal. People who got two shots only very reluctantly, after their employer issued a mandate, might finally balk at having to get a third. Maybe the feds will accommodate them by declaring that, although technically a person isn’t “fully vaccinated” until they’ve had three doses, two will suffice for satisfying the mandate.

Read this post from last night on why the CDC is looking at three doses as the proper regimen for “full vaccination.” There’s actual science to it, not just “keep boosting your antibodies unto eternity” panic. Some experts like Fauci have pointed to the fact that vaccines like the one for HPV don’t provide durable protection until you’ve had three doses rather than two. Researchers are beginning to suspect that the COVID vaccine might work the same way, especially since the first two doses are given with so little time in between. The first two may operate as a “single dose,” requiring a third for your body to develop a mature immune response to the virus’s spike protein.

An interesting question for researchers going forward will be whether people can generate durable protections with only two doses so long as those doses are spaced out much longer than the first two doses of the mRNA vaccine are currently — say, six months instead of three weeks. But for those of us who got doses one and two just a few weeks apart, there may be no way to build mature immunity without the third shot. Hence the CDC’s interest in figuring out what the proper “full” regimen is.