The U.S. government is buying 600,000 more doses of sotrovimab, the only the monoclonal antibody treatment expected to hold up against omicron, according to the drug makers, GlaxoSmithKline and Vir Biotechnology.

These doses are set to be delivered to the government over the next two months, the drug makers said.

This brings total sotrovimab doses purchased by the federal government to approximately 1 million.

Short supply of sotrovimab has been a growing concern for the White House as omicron spreads.

Until recently the government had not invested in buying bulk stock of sotrovimab, as it has with other monoclonal treatments. The government spent billions buying Regeneron and Eli Lilly's products to ensure there would be enough supply, but both of those may not hold up against omicron.

-ABC News' Sasha Pezenik

Florida reported 126,704 new COVID-19 cases this weekend, ABC Miami affiliate WPLG reported, citing CDC data.

Orlando opened a new testing site Monday at Camping World Stadium.

About 3,000 United Airlines workers currently have COVID-19, though none are in the hospital, the airline said.

On one recent day, one-third of all United Airlines employees at Newark Airport called in sick, the airline said.

United CEO Scott Kirby said the airline is cutting its near-term flight schedule to ensure they have enough staffing.

Kirby added that, prior to the vaccine requirement, United had one employee die each week from COVID-19.

-ABC News' Sam Sweeney

Some 20 million people across three Chinese cities are now under lockdown due to COVID-19 outbreaks.

Anyang, home to 5.5 million people, was the latest city to lock down its residents after discovering two cases of the fast-spreading omicron variant. Another 13 million people are under lock down in Xi'ian and 1.1 million in Yuzhou, with both cities still battling the highly contagious delta variant. Neither has reported any cases of omicron.

Meanwhile, restrictions have been imposed in the port city of Tianjin, about 80 miles southeast of Beijing, which is to host the 2022 Winter Olympics next month. The city's 14 million people are being tested for COVID-19 after two locally transmitted cases of omicron were detected over the weekend -- the first for mainland China.

-ABC News' Karson Yiu

Spain has reported more COVID-19 reinfections in a recent span of two weeks than it has during the rest of the pandemic, according to the latest data from a Spanish public health research institute.

Data from the Carlos III Health Institute shows there were 20,890 repeat infections reported in Spain from Dec. 22, 2021, to Jan. 5, 2022. That figure tops the 17,140 reinfections reported in the European country from the start of the pandemic in March 2020 to Dec. 22, 2021. The data includes confirmed, probable and possible cases.

Alfredo Corell, an immunology professor at Spain's University of Valladolid, told Spanish news site NIUS that the rising number of reinfections were due to the new and highly transmissible omicron variant.

"Prior to this variant, reinfections were anecdotal at the global level," Corell told NIUS. "Omicron has changed this paradigm."

In southern Africa, where the variant was first identified in November, preliminary research suggests that omicron is three times more likely to cause reinfections compared to other known variants of the virus, including the highly contagious delta. However, symptoms of reinfected individuals appear to be mild, according to Anne von Gottberg, a microbiologist at South Africa's National Institute for Communicable Diseases who is studying omicron.

"Previous infection used to protect against Delta," von Gottberg said during a press briefing on Dec. 2. "But now, with Omicron, that doesn't seem to be the case."