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More than 800,000 people have now died in the U.S. from COVID-19 as health officials continue to monitor the spread of the delta and omicron variants of the coronavirus.

Globally, more than 5.3 million virus-related deaths have been reported, according to data from Johns Hopkins University.

The year began with the COVID-19 death toll at about 350,000 in the U.S., which doubled once October hit. Since March 2020, nearly 50 million people have tested positive for the virus in the country, JHU data shows.

The grim milestone in the U.S. is especially frustrating to public health leaders and medical professionals on the front lines because vaccines have been available to all eligible Americans for nearly six months, with data showing the shots overwhelmingly protect against hospitalizations and death.

FILE - A white flag memorial installation honoring the nearly 27,000 Los Angeles County residents who have died from COVID-19 stands outside Griffith Observatory on Nov.18, 2021 in Los Angeles, Calif.

Now, as the year ends, the delta variant is fueling another wave of hospitalizations, court battles are brewing over vaccine mandates and fresh questions are swirling about the new omicron variant.

The rate of new cases in the country remains at an alarming level, health officials say. Data from the U.S. Centers for Disease Control and Prevention showed the 7-day moving average of COVID-19 cases hovering around 118,000. That’s up from late October where the average stood around 67,000.

U.S. health officials are urging people to get vaccinated and get a booster shot, which could become a routine practice. According to the CDC, more than 238 million people over the age of 5 have received at least one dose of the COVID-19 vaccine, representing 76.5 % of the demographic.

On Sunday, National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci said that Americans may "just have to deal with" the prospect of getting more coronavirus booster shots.

"If it becomes necessary to get yet another boost, then we’ll just have to deal with it when that occurs," Fauci said.

Meanwhile, health officials continue to monitor and see how COVID-19 vaccines hold up against the omicron variant which many scientists believe is milder than the delta variant — a strain that was responsible for a surge in cases over the summer.

In an interview with The Associated Press, Dr. Rochelle Walensky, director of the CDC, said the data is very limited and the agency is working on a more detailed analysis of what the new mutant form of the coronavirus might hold for the U.S.

"What we generally know is the more mutations a variant has, the higher level you need your immunity to be. ... We want to make sure we bolster everybody’s immunity. And that’s really what motivated the decision to expand our guidance," Walensky said, referencing the recent approval of boosters for all adults.

She said "the disease is mild" in almost all of the cases seen so far, with reported symptoms mainly cough, congestion and fatigue. One person was hospitalized, but no deaths have been reported, CDC officials said.

Some cases can become increasingly severe as days and weeks pass, and Walensky noted that the data is a very early, first glimpse of U.S. omicron infections. The earliest onset of symptoms of any of the first 40 or so cases was Nov. 15, according to the CDC.

The omicron variant was first identified in South Africa last month and has since been reported in 57 countries, according to the World Health Organization.

Last week, scientists in South Africa reported a small laboratory study that found antibodies created by vaccines were not as effective at preventing omicron infections as they were at stopping other versions of the coronavirus.

On Wednesday, vaccine manufacturer Pfizer said that while two doses may not be protective enough to prevent infection, lab tests showed a booster increased levels of virus-fighting antibodies by 25-fold.

The Associated Press contributed to this story. This story was reported from Los Angeles.