The FDA could authorize Moderna and Johnson & Johnson booster shots for some populations as soon as Wednesday. 

Meanwhile, the CDC independent advisory committee is meeting Wednesday to discuss vaccines in general. The committee is expected to debate Moderna and Johnson & Johnson on Thursday, discussing who boosters should be recommended for and if mixing and matching vaccines should be permitted.

A non-binding vote is expected at the end of Thursday.

The CDC director is expected to make the final recommendations shortly after the vote, which could come as soon as Thursday night or Friday morning.

-ABC News' Eric M. Strauss

New York City Mayor Bill de Blasio on Wednesday announced a COVID-19 vaccine mandate for all municipal workers.

The mandate is expected to include all employees from sanitation workers to office workers and will require some 161,000 workers to have their first dose by Oct. 29.

Municipal employees who do not get vaccinated will be placed on unpaid leave, and their future employment will be resolved in negotiations with individual labor unions.

Correction officers will face a later deadline of Dec. 1.

-ABC News' Aaron Katersky

Department of Homeland Security Secretary Alejandro Mayorkas has tested positive for COVID-19, a DHS spokeswoman confirmed to ABC News.

Mayorkas, who is fully vaccinated, "is experiencing only mild congestion," a statement said.

Mayorkas will work from home, the statement said. Contact tracing is underway.

There were no major White House officials deemed to be close contacts. "No White House principal has been determined to be a close contact of Secretary Mayorkas, given that the most recent contact was at the outdoor National Peace Officers’ Memorial Service, which took place outside of the 48-hour close contact window,” the White House said in a statement.

-ABC News' Luke Barr

A new CDC study found that the Pfizer vaccine was 93% effective against hospitalizations for adolescents ages 12 to 18 from July to September.

The researchers also found that nearly all (97%) of adolescents ages 12 to 18 who were hospitalized with COVID-19 were unvaccinated.

-ABC News' Sony Salzman

Coronavirus infections are steadily falling across the country, thanks to significant declines in highly populated states such as Florida, Texas, Louisiana and Mississippi.

The number of daily cases in the U.S. has dropped 50% since Sept. 1, with a 43% drop in hospitalizations and a 21% drop in daily deaths.

However, an uptick in cases in Northern states is causing some concern.

In recent weeks, coronavirus infections have been creeping up in several states in the Upper Midwest and the Northeast. Eight states — Alaska, Colorado, Idaho, Michigan, Minnesota, New Hampshire, New Mexico, and Vermont — have seen notable jumps in their case averages.

Experts have been warning for weeks that Northern states could begin to see upticks in the coming weeks as winter approaches, and people start to head indoors.

Alaska currently has the country's highest case rate, followed by Montana, Wyoming, Idaho, West Virginia, and North Dakota, which all with case rates above 400 per 100,000 people.

Daily deaths are slowly falling, but remain persistently high. The nation is still reporting an average of 1,250 new deaths each day, and over the last four days alone, the U.S. reported just under 7,000 confirmed COVID-19 deaths.

The death average is still about 6.5 times higher than in mid-July, when the national average had dropped to a near pandemic low of 192 deaths reported each day.

Nationally, hospitalization numbers have dropped to under 60,000 patients with COVID-19 currently receiving care, down from 104,000 patients in late August. Hospital admissions have also fallen by about 10.4% in the last week.

Approximately 113.5 million Americans remain completely unvaccinated. Just under 65.2 million of those people are over the age of 12. The other 48 million unvaccinated people are children under the age of 12.

— ABC News’ Arielle Mitropolous