Nearly 600 patients wait for hospital beds in Houston following surge in COVID cases

Dr. Richard Besser, president and CEO of the Robert Wood Johnson Foundation and former acting director of the CDC, told "Good Morning America" that he expects booster shots will "be available to people with immune disorders very quickly."

The FDA announced late Thursday that immunocompromised Americans – such as cancer patients, transplant recipients, people with HIV and people on immunosuppressant drugs -- will be able to get a third shot of Pfizer or Moderna.

But Besser stressed, "I think about this less as a booster shot" and more of "a recognition that for certain people with immune problems, two doses wasn’t enough" and "the third dose is necessary for them to get the same high level of protection that the rest of people do."

The CDC panel is expected to vote to recommend the third dose when it meets Friday at 11 a.m. and CDC Director Rochelle Walensky will likely sign off after a Friday afternoon vote.

Children's of Alabama reported a significant increase in the number of COVID-19 positive patients being treated at the hospital in recent weeks.

As of Thursday, the hospital said it is treating 22 COVID-19 positive patients, five of whom are on ventilators.

The hospital said in January, at the height of the last surge, their highest number of patients was 13.

"There are three proven ways to slow the spread of this highly transmissible strain of the virus: Vaccination for everyone 12 and up, masking, especially when indoors, and social distancing," the hospital wrote in a Facebook statement.

Immunocompromised Americans will be able to get a third shot of either of the mRNA vaccines, Pfizer or Moderna, the U.S. Food and Drug Administration announced late Thursday.

The booster 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.

"The country has entered yet another wave of the COVID-19 pandemic, and the FDA is especially cognizant that immunocompromised people are particularly at risk for severe disease," acting FDA Commissioner Janet Woodcock said in a statement. "After a thorough review of the available data, the FDA determined that this small, vulnerable group may benefit from a third dose of the Pfizer-BioNTech or Moderna Vaccines."

For more, read ABC News' full story on the authorization.

-ABC News' Cheyenne Haslett

The Supreme Court rejected a plea from a group of Indiana University students to stop the university's requirement that all students be vaccinated against COVID-19.

Justice Amy Coney Barrett, who is tasked with emergency petitions from that region of the country, did not give a reason behind her ruling Thursday.

It was the first case about vaccination requirements to reach the Supreme Court. Both a federal district judge and a unanimous panel of the U.S. Court of Appeals for the Seventh Circuit had previously rejected the request that the university’s requirement be put on hold while the issue was further litigated.

In June, Indiana University administrators announced that students and employees would have to verify their vaccination status unless they applied for a medical or religious exemption.

The lawsuit alleged that the university violated students' rights and that if they did not comply, they would face "the threat of virtual expulsion from school."

-ABC News' Will Gretsky and Erin Schumaker