With the Oct. 21 approval of CDC Director Rochelle Walensky, MD, booster shots of all three COVID-19 vaccines are now available for about 70 million Americans.
The FDA and CDC made their decisions to approve boosters based on several clinical trials that suggest efficacy of the vaccines wanes slightly over time and that immunity levels rise after an extra dose.
The agencies are also letting people choose which vaccine they want for a booster dose, giving more flexibility to providers and vaccination sites. Dr. Walensky said Oct. 22 that the CDC won't articulate a preference for who should get which booster, according to The Hill.
She added that the CDC won't change the definition of fully vaccinated based on whether or not someone has received a booster shot.
Here's a breakdown of eligibility for each COVID-19 booster shot:
Pfizer
Who is eligible: People ages 65 and older, adults at high risk of severe COVID-19 infection or adults whose jobs put them at a higher risk of COVID-19 infection.
When they can get a booster: At least six months after their first two doses.
The supporting data: Pfizer conducted a phase 3 trial involving more than 10,000 participants ages 16 and older who received two doses of its vaccine. Half of the participants received a booster dose, and half received a placebo.
Participants who received a booster dose had higher immunity levels than participants who did not. The study found the booster doses restored immunity to the same high levels achieved after their second dose, as the research team observed the vaccine's efficacy to be 95.6 percent among the booster group.
Moderna
Who is eligible: People ages 65 and older, adults at high risk of severe COVID-19 infection or adults whose jobs put them at a higher risk of COVID-19 infection.
When they can get a booster: At least six months after their first two doses.
The supporting data: The FDA analyzed immune response data from 149 participants ages 18 and older who received a booster dose at least six months after their second dose. The agency compared the data to the immune responses of 1,055 study participants after completing their two-dose series, finding the additional shot raised immunity levels.
The FDA also examined additional data from Moderna comparing the rates of COVID-19 cases accrued from July through August, when the delta variant spread rapidly. The agency found the data suggested the vaccine's efficacy wanes over time.
Johnson & Johnson
Who is eligible: All Johnson & Johnson vaccine recipients ages 18 and older.
When can they get a booster: Two months after their first shot.
The supporting data: The FDA evaluated immune response data from 39 participants ages 18 and older, including 15 people who were 65 and older. The data showed their immunity levels rose when they received a booster dose about two months after their first dose.
About 9,000 clinical trial participants in total have received two doses of Johnson & Johnson's shot administered at least two months apart, and of those, about 2,700 have had at least two months of safety follow-up after the booster dose. The FDA said no new safety concerns have been observed.