Nearly 100 million people nationwide are immediately eligible to receive Covid booster shots after the Centers for Disease Control and Prevention authorized extra doses of Moderna and Johnson & Johnson’s vaccines Thursday night.

The agency’s decision also enables fully immunized people to pair their boosters with doses from different manufacturers after research from the National Institutes of Health showed it was safe and effective to mix and match vaccines. Pfizer and BioNTech’s boosters were widely cleared for use in the U.S. on Sept. 24.

Some 11.6 million individuals across the country have already received their boosters, and the CDC’s approvals opened them up to tens of millions of more people. But not everyone is eligible. Here is who’s allowed to get the extra doses in the U.S. based on their first round of shots:

More than 47 million Pfizer vaccine recipients who received both shots at least six months ago became eligible for a booster Friday, according to data presented Thursday before the CDC’s advisory committee. That includes:

• Anyone 65 and older.
• All adults age 18 to 64 who have cancer, dementia, diabetes, heart disease, HIV and other medical conditions that increase their likelihood of Covid complications.
• Anyone 18 or older who live or work in a long-term care facility, homeless shelter and prison or other congregate setting.
• Front-line personnel 18 or older who are at a higher risk of Covid exposure due to their job, including first responders, teachers, supermarket staff and mass transit employees.

More than 39.1 million Moderna vaccine recipients who received both shots at least six months ago became eligible for a booster Friday, according to the CDC presentation. The CDC adopted the same criteria for Moderna recipients as Pfizer since the two companies use the same mRNA technology in their Covid vaccines. They include.

• Anyone 65 and older.
• All adults age 18 to 64 who have cancer, dementia, diabetes, heart disease, HIV and other medical conditions that increase their likelihood of Covid complications.
• Anyone 18 or older who live or work in a long-term care facility, homeless shelter and prison or other congregate setting.
• Front-line personnel 18 or older who are at a higher risk of Covid exposure due to their job, including first responders, teachers, supermarket staff and mass transit employees.

The CDC adopted a slightly different criteria for J&J’s one-shot Covid vaccine, making almost 13 million recipients eligible as of Friday. That includes

• All adults who were vaccinated with J&J’s Covid vaccine at least two months ago, instead of six months with Pfizer and Moderna.
• All adult J&J recipients are eligible for a booster even if they don’t have underlying medical conditions or work in a profession or live where there’s a higher risk of Covid.