CNN  — 

There’s a new kind of Covid-19 shot coming to a pharmacy or clinic near you.

The US Food and Drug Administration and US Centers for Disease Control and Prevention signed off on updated boosters that target the original strain of the coronavirus as well as the Omicron subvariants BA.4 and BA.5. The hope is that these shots will improve protection against the currently circulating viruses that cause Covid-19.

Here’s everything you need to know about the new bivalent boosters and who can get them.

How are these new bivalent vaccines different?

The new bivalent vaccines carry instructions to help our cells make defenses against two strains of the virus that causes Covid-19. The shots direct cells to make antibodies that bind to certain parts of the spike proteins from both the original strain of the SARS-CoV-2 virus and the BA.4 and BA.5 Omicron subvariants, which share an identical spike.

BA.4 and BA.5 are the dominant variants in the United States, where there’s an average of 91,000 new infections each day.

“These are vaccines that are made, manufactured and delivered identically to the Covid mRNA vaccines that most of us have already gotten,” said Dr. Gregory Poland, who leads the vaccine research group at Mayo Clinic in Rochester, Minnesota. “In a sense, you’ve just changed the blueprints.”

Having twice the blueprints doesn’t mean you’re getting twice the dose of active ingredients, though.

“The total mRNA content – the business part of the vaccine – that leads to the immune response is the same amount,” said Dr. William Gruber, senior vice president of vaccine research and development at Pfizer, which makes one of the updated vaccines.

Pfizer’s booster is a 30-microgram dose that contains 15 micrograms of mRNA against the ancestral strain and 15 micrograms against the BA.4 and BA.5 variants. It is authorized for people as young as 12.

Moderna’s bivalent booster is a 50-microgram dose, with 25 micrograms of mRNA designed to fight the ancestral strain of the coronavirus and 25 micrograms of mRNA designed to fight the BA.4 and BA.5 variants. It’s authorized for people 18 and older.

The earlier mRNA shots are still the first two shots a person will get, but they’re no longer authorized for use as boosters in people age 12 and older.

Where can I get an updated Covid-19 booster?

Millions of vaccines are now shipping to tens of thousands of sites across the country. These include community health centers, health departments and pharmacies.