The U.S. is forecast to have almost 500,000 COVID-19 deaths by mid-February, incoming CDC Director Dr. Rochelle Walensky said on CBS’ "Face the Nation" Sunday morning.

She added, "That doesn't speak to the tens of thousands of people who are living with a yet uncharacterized syndrome after they've recovered."

Walensky, who was appointed by the Biden administration, believes that 100 million more doses of the vaccine will be available within the next 100 days.

"That is what the president-elect has promised," she said. “It will be a hefty lift, but we have it in us to do that.”

ABC News’ Brian Hartman contributed to this report.

People seeking COVID-19 vaccines in Houston were sent away from Minute Maid Park after appointments were overbooked.

The Houston Health Department announced Saturday that it had run out of vaccines by 6 p.m. after it had administered 5,451 doses at the site, where the line wrapped around the building, ABC Houston station KTRK reported. Several people left without getting vaccinated.

Houston Health Department Stephen Williams said during a press conference Saturday he warned the mayor that there wouldn’t be enough doses to last the week.

The city received “a little” over 30,000 doses, Houston Mayor Sylvester Turner said in a statement.

-ABC News’ Ahmad Hemingway contributed to this report.

Prince William championed the effort of the NHS, the U.K.'s health agency, in delivering the COVID-19 vaccine in a video posted to Kensington Royal's Twitter account Saturday night.

The video included several health care professionals on a Zoom call, along with the Duke of Cambridge, talking about distributing and delivering the vaccine.

"This is because we have a world-leading NHS, this is because we have the right people, the right research and development here," William says in the video.

William also encourages people to get the vaccine when they are eligible, noting his "grandparents" -- Queen Elizabeth and Prince Philip -- got the vaccine already. The palace said last week that Elizabeth, 94, and Philip, 99, had gotten the vaccine.

"My grandparents have had the vaccine and I'm very proud of them for doing that," he says in the video. "So it's really important that everyone gets their vaccine."

Los Angeles County, the hardest hit region in the country right now, announced it has crossed 1 million confirmed cases of COVID-19 on Saturday.

The county has identified 1,003,923 cases since the start of the pandemic -- the first county in the country to cross the mark. Only four states outside of California have met that ignominious total. The county announced 253 new deaths and 14,669 new cases on Saturday.

There are currently 7,597 people hospitalized in LA County with COVID-19 -- down slightly from days earlier when the total crossed 7,900.

Also of concern, the county identified its first case of the so-called U.K. variant on Saturday. The case was discovered in a man who was recently in LA, but has since traveled to Oregon, where he is isolating, the health department said.

"The presence of the U.K. variant in Los Angeles County is troubling, as our healthcare system is already severely strained with more than 7,500 people currently hospitalized," said Dr. Barbara Ferrer, director of public health. "This more contagious variant makes it easier for infections to spread at worksites, at stores, and in our homes."

There had already been 40 cases of the variant, officially called the B.1.1.7 variant, detected in California.

Seychelles, an island nation of just under 100,000 people, has begun immunizing its population against COVID-19 with a vaccine developed by China’s state-owned pharmaceutical company, Sinopharm.

Seychelles President Wavel Ramkalawan became the first African head of state to receive the Sinopharm vaccine on Sunday, as the country officially launched a national COVID-19 immunization campaign -- the first in Africa to do so. The Seychelles Ministry of Health began administering the shot to priority groups on Monday, starting with health care professionals and other front-line workers, according to a press release from the president’s office.

Last month, China authorized Sinopharm's vaccine for general use after the company announced that preliminary data from late-stage trials had shown it to be 79.3% effective. The shot is administered in two doses.

The United Arab Emirates donated 50,000 doses of the Sinopharm vaccine to Seychelles. India offered 100,000 doses of another COVID-19 vaccine developed by England’s University of Oxford and British-Swedish pharmaceutical giant AstraZeneca, which are due to arrive in Seychelles at the end of the month, according to the president's office.

“With such a robust vaccination campaign, Seychelles aims to be the first country in the world to vaccinate at least 70% of its over 18 population,” Ramkalawan said in a statement Sunday. “From there, we will be able to declare Seychelles as being COVID safe. This will allow us to reopen our economy.”

Seychelles, an Indian Ocean archipelago located off the coast of East Africa, has reported 508 confirmed cases of COVID-19 since the start of the pandemic, including at least one death, according to the latest data from the Africa Centers for Disease Control and Prevention.