Hey readers,

This week, Vox welcomed three new Future Perfect fellows: Muizz Akhtar, Siobhan McDonough, and Miranda Dixon-Luinenberg. We’re incredibly excited to have them on board — look out for their first Future Perfect stories in the coming weeks!

Now on to the newsletter …

The big Covid topic on everyone’s minds is boosters.

On Friday morning, the FDA authorized Pfizer and Moderna booster shots for all adults 18 and up. Any day now — perhaps later today — the CDC is expected to follow suit and announce that every fully vaccinated person 18 and above at least six months removed from their last shot can finally get a booster shot for Covid-19.

The long-awaited decision comes after months in which the boundaries of who can get a booster have been widening. The Biden administration first announced its plans to make boosters widely available in August. Since then, we’ve seen the rollout of boosters to Pfizer and Moderna recipients over 65, and those who are 18 and up who are immunocompromised or at high risk of infection. All adult Johnson & Johnson one-dose recipients have also been approved.

The fact is the federal government has been lagging on this front. Several states have already gotten ahead of the federal government by approving boosters for adults: Colorado, California, New Mexico, and Arkansas, among others, have all moved in the last few weeks to declare nearly all adults eligible. And based on anecdotal accounts, even adults not eligible yet have been able to get a booster.

That has left people anticipating official federal guidance that anyone who wants a booster can get one — and it has also fostered confusion over what exactly the US’s public health game plan is and whether getting the booster is the right personal choice for any given person.

Those questions will only loom larger if and when the CDC finally makes its move, as expected. Here’s how to help you think through the booster situation.

I’m healthy and not at risk for serious disease. Should I get a booster?

Personally, this describes my situation — and I’m getting one.

If you got two shots of the mRNA Pfizer/BioNTech or Moderna vaccines, as I did, you’re already fairly well-protected from severe Covid outcomes. The main thing a booster does is make you less likely to get infected and (mildly) sick — but that’s still good to have.

We have a lot more data on these vaccines than we did when they were first approved. We know that they generally remain very effective against severe illness and death even a year after one is fully vaccinated. But they do wane in effectiveness against infection. Six months after your second dose, the vaccine is less protective against catching Covid-19.

That’s because antibody levels in the blood decline over time. Experts disagree on how much people should worry about that. Dr. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia, told me that a healthy, functioning immune system gradually prunes blood antibodies for infections the body hasn’t encountered, but it doesn’t necessarily mean you won’t fight off Covid-19 just fine (likely suffering only mild, maybe even unnoticeable illness).

There’s a fair debate to be had about whether preventing infection, if illness is likely to be mild, is all that important as a public health priority. But even though I won’t get all that sick if I get Covid-19 because I’m fully vaccinated, I prefer not to get it at all. The booster does reduce my risk of becoming infected with Covid-19 — period. For me, that’s sufficient to take a booster, especially given that I didn’t have bad side effects from the first two shots.

This lukewarm recommendation becomes a much stronger one if you are at elevated risk from Covid-19. If your immune system functions less well or you work in a high-risk setting, then a booster shot might be needed just to get your immune system to the level of readiness that healthy people were at after two shots. That’s well worth it.

And if you got Johnson & Johnson, you should definitely get a booster (something which the CDC has already approved) to prevent some waning in vaccine effectiveness.

If I’m healthy and get a booster, am I taking a dose away from someone who needs it more?

A lot of these questions are complicated, but here’s one we can be pretty sure of: Your booster shot, if you choose to get one, is very likely not directly coming at the expense of other people, experts told me.

The concern here stems from the fact that many people in the US will be getting their third shot when about half of the world hasn’t had even one shot. That’s not just an injustice and a humanitarian wrong, it’s also strategically foolish: Virus variants can develop more easily when Covid-19 cases are high, and vaccines are the most effective way to lower them.

If skipping a booster would get that shot to someone in a poor country instead, I’d prefer to do that.

But that’s not really how vaccine allocation works. Many months ago, the US placed orders with Moderna and Pfizer for millions of doses of their vaccines. Other countries and international organizations did the same.

Those orders, experts told me, are being fulfilled in the order they were placed — so if Moderna is committed to delivering 20 million doses to the US first, then 10 million to France next, that’s the order they will send them. And if the US orders additional doses now in response to increased demand from booster-getters like us, that request will be at the back of the queue.

Not getting your booster won’t get that shot to people in other countries who need them more. What might help, Amanda Glassman, senior fellow at the Center for Global Development, told me, is queue-swapping: The US formally ceding its place in line to other countries that need it more or to Covax, the international alliance to vaccinate the world.

UNICEF has called on the US and other rich countries to do just that. The US also could — and should — donate excess doses (it has donated roughly 200 million of them so far), but it’s unclear how demand for boosters this fall and winter will affect the odds of new donations of excess doses in the future; the US plans to fulfill its remaining unfulfilled pledges of donating more than a billion doses through purchase orders for COVAX currently in the queue.

If you’re frustrated, like I am, that millions of vaccines are going unused in the US while they’re badly needed elsewhere, you should absolutely push for the US to give up its place in line. But skipping a booster shot won’t change how many doses Moderna or Pfizer will deliver to the US before they move on to the next country on their list. And within the US, we have plenty of supply of mRNA vaccines at this point — so getting a booster isn’t taking one from your neighbors either.

—Kelsey Piper, @kelseytuoc