Though considered milder than other coronavirus variants, omicron has infected so many people that it has driven the number of daily deaths beyond where it was last spring, before vaccines were widely available, according to Washington Post data.

Omicron has been particularly lethal to people over 75, the unvaccinated and the medically vulnerable, according to doctors and public health officials. The soaring death toll also illustrates why experts pleaded with the public to beware of the highly contagious variant even though it is less virulent than others.

“That feels quite jarring to people who may have assumed omicron is generally on a per-case level less severe and given the fact we have vaccinated at least some portion of the country,” said Jennifer Nuzzo, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health. “Even if on a per-case basis fewer people develop severe illness and die, when you apply a small percentage to a very large number, you get a substantial number.”

Yet the seven-day average of deaths during the omicron surge has reached 2,600 in recent days, climbing past the late September peak of about 2,000 average daily fatalities during the surge of the more dangerous delta variant, according to Washington Post tracking. The ranks of hospitalized patients with COVID-19 reached record highs in January. Coronavirus deaths lag hospitalizations.

More than 900,000 Americans have died of coronavirus.

The latest victims tend to be older, according to a Washington Post review of federal data. Nearly half of the deaths in January 2022 were among those 75 and older, compared to about a third in September.

Experts theorized hospitalizations and deaths during the delta surge skewed younger because of high rates of vaccination among senior citizens and the delta variant appearing to cause particularly severe illness among middle-age adults compared to earlier surges. Now the age distribution of deaths resembles the deadliest stage of the pandemic last winter, when more than 3,000 were dying a day.

Jason Salemi, an epidemiologist at the University of South Florida College of Public Health, said Florida has seen similar age trends with seniors making up about 85 percent of deaths last winter, about 60 percent during the delta surge and back to about 80 percent in the omicron surge. He suspects factors include seniors who were recently vaccinated during the delta surge but did not get boosters ahead of omicron and higher raw numbers of seniors infected in the latest wave.

“Omicron may be less severe for younger people, but it will still find vulnerable seniors in our community,” Salemi said. “That vaccination back in February isn’t as effective now if you aren’t boosted.”

Several states including Illinois are seeing deaths on par with last winter’s peak.

Illinois averaged more than 150 deaths a day in the last week of January, compared to the all-time peak of about 180 in December 2020. But Illinois also saw the lowest case-to-death ratio of any coronavirus wave, a spokeswoman for the state health department said.

Advocate Aurora Health, Illinois’ largest health system, has seen an in-hospital mortality rate for COVID-19 patients decline from about 20 percent at the start of the pandemic to under 2 percent now.

“You are flooding the system with so many patients that the crude number of deaths is going to be higher, but what we really focus on is the death rate,” said Robert Citronberg, Advocate Aurora Health’s executive medical director of Infectious Disease and Prevention. He noted nearly all the latest deaths have been among the unvaccinated.

“There’s also a big group of patients who are politically motivated and don’t want to be told what to do,” Citronberg said. “They are willing to die from this disease because they don’t want to be told what to do, and it’s basically crazy.”

Chicago recorded more than 1,000 COVID-19 fatalities in the last two months, almost matching a December 2020 daily peak of about 30 deaths in mid-January. About half of the recent victims are Black in a city that’s about a third Black. And 27 of the dead were adults under the age of 40.

Public health officials have also stressed death rates barely budged among the vaccinated and boosted while surging for older unvaccinated adults. The city reported an age-adjusted death rate peaking at 14 per 100,000 for the unvaccinated around January 22 compared with about 1 per 100,000 for the boosted.

“It’s been challenging because it goes up against the national narrative that omicron is nothing dangerous,” Allison Arwady, commissioner of the Chicago Department of Public Health, said. “I don’t think society wants to be a place where we are talking about 30 deaths a day.”

Public health officials like Arwady are facing similar challenge in trying to communicate the conflicting nature of omicron: It poses a lower risk to individuals, but a greater risk to society when the vulnerable face the highest likelihood yet of contracting the virus during a massive surge.

Wes Stubblefield, a northern and northeastern district medical officer for the Alabama Department of Public Health, says recent deaths are concentrated among those older than 75 even as cases are concentrated among the 25-49 age group. Deaths are still rising in the South, which started experiencing omicron surges later than the Northeast, although they tend to be lower than during the delta surge when unvaccinated people were at high risk.

“This disease is still killing Alabamians. It’s still a severe illness; it’s still more deadly than other common respiratory illnesses; it’s something people should take very seriously, especially those who have underlying conditions,” Stubblefield said. “What we’ve tried to mention to people is that people can still spread disease to their loved ones even if they are healthy.”

Hospitals are seeing the consequences of the massive spread in the patients dying in their intensive care units as the most vulnerable are unable to fight off the virus.

While the University of Pittsburgh Medical Center has seen fewer of its hospitalized patients die in the most recent surge, those who do are older than their counterparts during the delta surge, said Oscar C. Marroquin, the medical system’s chief health care data and analytics officer.

During the previous surge, the average age of patients who died was 68.4. During the omicron period, it is 74.2, according to Marroquin’s data.

Most of the current fatalities are among unvaccinated patients and a significant number are immunosuppressed because they are undergoing chemotherapy, have received an organ transplant or have a disease that harms the immune system, Marroquin said.

Other hospitals have been raising alarms about immunocompromised patients whose systems struggle to generate antibodies to fight off coronavirus even after vaccination. Colin L. Powell, the former U.S. Secretary of State, was one of the highest profile examples when he died of COVID-19 complications while also being treated for a blood cancer that severely impairs the immune system.

Andrew Myers, director of inpatient COVID care at Tampa General Hospital, said the record levels of patients his hospital has seen in the latest outbreak has included more immunocompromised patients who take the virus seriously but had a harder time dodging omicron.

When a variant like omicron rapidly spreads through the population at once and requires less exposure time to infect, an immunocompromised person is more likely to get infected when a loved one visits or during routine activities.

“It’s really unfortunate for them when something like this is spreading because if you are unable to have that extra protection, it makes life a whole lot more difficult,” Myers said.

“Even if you feel fine as a 25-year-old or 35-year-old, one, you are taking a chance, a small chance,” he added. “But two, you don’t know who else you can infect. You don’t know if that lady sitting next to you outside or the lady you work with at the store are immunocompromised of if they have someone at home who is immunocompromised. It’s a butterfly effect.”

The recent uptick in coronavirus deaths also likely includes residual deaths from delta surges which were just starting to hit parts of the country including New England in late fall before omicron became the dominant strain of the virus.

“We don’t know what kind of variant a person sitting in front of us has and because we keep people in the hospital alive for weeks, many of the deaths occurred over last several weeks were residual delta infections,” said Shira Doron, hospital epidemiologist at Tufts Medical Center, where nearly 30 patients died in December and January.

Some hospitals have also seen growing numbers of patients infected with COVID-19 when they died of other causes because of the sheer volume of infections. Such deaths would not have COVID-19 listed as a primary cause and drive up the latest numbers, but they do reflect a changing dynamic for health care in the pandemic.

“It’s not a black or white phenomenon,” said John Rimmer, chief medical officer of CarePoint, which operates three hospitals in New Jersey. “COVID has become a co-morbidity many patients are presenting with. Just like someone with diabetes may not heal as well, someone with COVID may not heal as well.”