Immunocompromised Americans are one step closer to getting additional vaccine protection after the CDC's advisory panel voted unanimously on Friday to recommend an extra dose for roughly 7 million people.

       The panel's vote was the latest step in the process initiated by the Food and Drug Administration's announcement late on Thursday night that immunocompromised Americans will be able to get a third shot of either of the mRNA vaccines, Pfizer or Moderna.

       The next and final step is for CDC Director Rochelle Walensky to issue official guidance on the use of an extra dose.

       The additional does, if approved, will be targeted specifically for people who did not have an ideal immune response to their initial vaccines, which has proven to be the case for many cancer patients, transplant recipients, people with HIV and people on immunosuppressant drugs.

       Instead of the more than 90% protection from the vaccines that's normally found in healthy people, vaccine effectiveness in immunocompromised people can be as low as 59% to 72%, the CDC said.

       Some immunocompromised people even had no immune response to the vaccines -- a disappointment considering the high risk they have for getting severely ill from the virus.

       For example, in one U.S. study, 44% of breakthrough cases that led to hospitalization were in immunocompromised people. An Israeli study found it was around 40%.

       But the Centers for Disease Control and Prevention data shows that a booster shot could increase antibodies in an immunocompromised person by up to 50%.

       Mary Altaffer/AP, FILE

       A health care worker fills a syringe with the Pfizer COVID-19 vaccine, July 22, 2021, at the American Museum of Natural History in New York.

       "COVID-19 disease in immunocompromised people is an important public health problem. The anticipated desirable effects of an additional dose of mRNA vaccine are large, and undesirable effects expected to be minimal, favoring the intervention," Dr. Kathleen Dooling, a medical officer at the CDC, said at the meeting on Friday.

       The CDC estimated about 7 million people, or 2.7% of the population, fit into the category of moderate or severely immunocompromised. But there is no plan to require people to prove their conditions before receiving a third shot, either by prescription or a doctor's note -- it will be a matter of "self-attesting."

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       CDC officials suggested that the third shot should come at least 28 days after finishing the primary two-dose series and recommend that people stick with the same vaccine they initially got, be it Pfizer or Moderna, though swapping the vaccines in instances where there isn't ample supply is "permitted."

       Callaghan O'hare/Reuters

       A person receives a COVID-19 vaccine at Floyd's Family Pharmacy as cases of the coronavirus disease (COVID-19) surge in Ponchatoula, Louisiana, Aug. 5, 2021.

       Immunocompromised people who got the Johnson & Johnson vaccine are not yet eligible for additional shots, but the CDC and FDA said they're doing research and hope to provide more guidance soon.

       The CDC also assumes the vast majority of immunocompromised people got mRNA vaccines because only 12 million people nationwide have gotten the Johnson & Johnson vaccine, while 149 million have gotten Pfizer or Moderna shots.

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       "We think that at least there was a solution here for the very large majority of immunocompromised individuals and we believe that we'll probably have a solution for the remainder in the not too distant future," Dr. Peter Marks, vaccine chief for the FDA, said at the meeting.

       Experts and officials have been clear that this third shot for immunocompromised people is separate from booster shots for the general public, which people are expected to need as the protection from the vaccines wane over time. But the FDA and CDC, which are monitoring immunity in multiple groups of people across the country, said the U.S. isn't there yet.

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       "As we’ve previously stated, other individuals who are fully vaccinated are adequately protected and do not need an additional dose of COVID-19 vaccine at this time," acting FDA Commissioner Dr. Janet Woodcock said in a statement Thursday. "The FDA is actively engaged in a science-based, rigorous process with our federal partners to consider whether an additional dose may be needed in the future."