New Covid-19 vaccine boosters are available. Here’s what you need to know.

The wait is over: Updated versions of Covid-19 booster shots have received a green light from the Food and Drug Administration, and the Centers for Disease Control and Prevention now recommends them for all Americans age 12 and older.

This push for new, updated boosters is coming at a good time. Health officials are warning of another likely spike in Covid-19 transmission this fall as people head back indoors once again.

The reformulated booster doses of the mRNA vaccines from Pfizer/BioNTech and Moderna are “bivalent.” That means they target the original version of SARS-CoV-2 as well as the newer omicron variant. The hope is that when administered as boosters, these new shots will increase protection against the latest mutations in the virus, and head off a rise in hospitalizations and deaths.

With new vaccines come new questions about what makes them better, who’s eligible, and when to get one. To help people understand when, why, and how to get their booster doses, we’re answering some of those questions here.

Let’s get into it.

Who’s eligible for the new coronavirus boosters?

According to the CDC’s recommendations, everyone 12 and older should get an updated booster shot. People 18 and over can get either a Pfizer or Moderna shot, while teens between 12 and 18 should get a Pfizer shot, as the FDA hasn’t reviewed Moderna data for younger teens yet. The CDC’s guidance suggests that getting either booster, regardless of what prior vaccines you received, is fine, although there’s no hard data yet on mixing and matching.

The CDC’s Advisory Committee on Immunization Practices did not recommend updated boosters for kids younger than 12 because manufacturers haven’t yet submitted data on these age groups for the FDA’s review. That will likely happen later this fall. Meanwhile, younger kids (between 6 months and 12 years) can get the original formulation of the vaccines.

How will I know if my booster is updated for the omicron variant?

As the bivalent boosters roll out, the older, monovalent boosters will become unavailable, so you won’t have to decide whether to get one or the other.

For people 12 and older, it’s all bivalent boosters for now — at least, until next-generation vaccines (like universal coronavirus vaccines and intranasal vaccines) become available in the US, and that’s unlikely to happen in the next few months.

How long after my last vaccine (or a recent Covid-19 infection) should I get a new booster shot?

Covid-19 infection and vaccination both provide some level of protection against future infections, which can last for a few months. During those months, your memory B cells — your immune system’s antibody factories — don’t respond as robustly to Covid-19 booster shots, perhaps because they’re busy fine-tuning the quality of the antibodies they’re producing in response to the original infection or vaccine.

Whatever the reason, this means that if you were recently infected with or vaccinated for Covid-19, you should take a beat before getting your bivalent booster shot.

How many months? Regardless of whether you were recently boosted or recently got Covid, the…