Booster shots to prevent COVID-19 infection will soon become a reality nearly 10 months after Pfizer-BioNTech's vaccine was first authorized and rolled out to health care workers in the U.S.
The Food and Drug Administration authorized booster shots Wednesday for people 65 and older, younger adults with underlying health conditions and those in jobs that put them at high risk for COVID-19 at least six months after their second dose.
So, what does that mean?
On Thursday, a Centers for Disease Control and Prevention committee is meeting to figure it out. The advisory panel, called the Advisory Committee on Immunization Practices, will decide how to implement expanded access. CDC Director Dr. Rochelle Walensky is expected to quickly sign off on whatever the committee decides.
While it's still unclear and information continues to change, here's who may be eligible for the shot in a few days.
People who are 65 and older
Because the immune system's effectiveness declines with age, people older than 65 are likely to get the biggest benefit from a booster dose.
Now, here come the exceptions.
People 18 to 64 with underlying health conditions
People who are severely immunocompromised and might not have gotten protection from the first two doses have been able to get a third dose for the past six weeks or so. This includes people who may have immunocompromising conditions or are taking immune-suppressing medications, including those taken after an organ transplant.
It's important to note this group of people got a "third dose" and not a "booster dose," said Dr. Sachin Nagrani, medical director for Heal, a health care service offering home doctor visits across the country.
A third dose implies the first two doses did not achieve intended immunity whereas a booster dose means the immunity may have waned over a period of time.
"If you needed a third dose from being immunocompromised, that's because you never actually got immunity from the two shots," he said.
Some underlying health conditions that may require a booster shot at least six months after the second dose of the vaccine could include anybody who has had cancer, chronic kidney disease, chronic lung disease including moderate to severe asthma, diabetes and heart disease, Nagrani said.
The CDC's vote on Thursday would clarify who exactly will qualify for a booster shot.
People 18 to 64 at high risk of infection at their work
The FDA has indicated that people whose jobs put them at extra risk for infection would also be eligble.
This group may include health care workers, teachers and day care staff, grocery workers and those in homeless shelters and prisons, "among others," said acting FDA Commissioner Dr. Janet Woodcock in a statement released Wednesday.
"As we learn more about the safety and effectiveness of COVID-19 vaccines, including the use of a booster dose, we will continue to evaluate the rapidly changing science and keep the public informed," she said.
As hospitalizations continue to climb among high COVID-19 transmission, health care systems cannot afford health care workers calling out sick. They're also at highest risk of infection since they treat COVID-19 patients.
Although the first rollout of vaccines in December 2020 only included health care workers, Nagrani speculates the FDA is "casting a wider net" and authorizing boosters to essential workers outside of health care "because the infrastructure to deliver the vaccine is already in place."
Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.
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This article originally appeared on USA TODAY: Who is considered 'high risk' for COVID booster shots? What to know