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

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

New Orleans will soon require proof of COVID-19 vaccination or a recent negative test for many indoor activities, city officials announced Thursday.

The order goes into effect Monday and includes bars, restaurants, breweries, gyms, fitness centers, sports stadiums, music halls and casinos. Enforcement will start Aug. 23, Mayor LaToya Cantrell said.

The Saints stood behind the new guidelines, which will require that people show their vaccination card or verified digital proof of vaccination, or a negative PCR test taken within 72 hours.

"These rules allow for full capacity on game day, and we must comply with those regulations to safely return to full capacity for the first time in more than a year and a half," team officials said in a statement. "We are committed to doing everything we can in the current environment to protect your health and safety while at the same time providing the best game day experience in the NFL."

Officials in San Francisco made a similar announcement earlier Thursday that goes into effect Aug. 20.

People who received Moderna's COVID-19 vaccine still produced antibodies six months later against several variants of concern, including delta, a new study found. 

The study, which was published in the journal Science Wednesday, only looked at antibody response at least six months out. The antibody levels, which are one piece of the overall immune response, waned over time but they were still there after six months. 

This study is part of a mounting body of evidence suggesting that vaccines are likely still to protect against new variants many months after initial vaccination. The Food and Drug Administration is expected to recommend booster shots for immune-compromised people this week. 

-ABC News' Sony Salzman