Latest numbers show jump in COVID-19 deaths as expected winter surge arrives

While the deaths are still “too many,” said Sam Scarpino of Northeastern University, “we’re doing a lot better than last year for sure.”

Most of those who are dying are older, and indeed those over age 80 make up a growing proportion of the victims as new subvariants steal the last years of many a grandparent and great-grandparent.

Scarpino believes this suggests that younger people, the majority of whom have immunity — from either vaccination or previous infection, or both — are able to fight off the virus better than older people whose immune systems are weaker. Older people may also be suffering from the many other respiratory infections going around, possibly further weakening their ability to survive COVID-19.

Massachusetts has done a better job than many other states in vaccinating the elderly, with 59 percent of those age 65 and older having received the bivalent booster, the most recent version of the vaccine that protects against recent variants as well as the original form of the virus. Nationwide, only 38 percent in that age group have received the bivalent booster. In Massachusetts, 28 percent of people age 5 and older have received the shot.

But that’s not enough, Scarpino said.

“What we need to do is get booster numbers up across the board,” he said. “There’s this vulnerable population out there that really needs protection from the rest of us.”

The new variants of the virus are more effective at evading vaccines’ protection. “You really need to have the bivalent booster to have much protection against infection,” said Scarpino, who works on infectious disease surveillance as director of artificial intelligence and life sciences at Northeastern‘s Institute for Experiential AI.

The number of people hospitalized with COVID has been rising steadily since Thanksgiving, as has the amount of virus detected in waste water in communities around Massachusetts. On Jan. 3, there were 1,336 people hospitalized with COVID-19, the highest number since February 2022. But a year ago, COVID-19 was the main reason half the those patients were in the hospital; the rest were diagnosed with COVID-19 after being admitted for another reason. Currently about one-third of hospitalized patients were admitted with COVID-19 as their primary diagnosis.

On Friday, the US Centers for Disease Control and Prevention elevated the “community risk level” for Suffolk County from medium to high. Now about half the state is labeled “high,” an indication that COVID-19 infections are having an impact on the health care system. When levels are high, residents are advised to wear masks in public places, and people in danger of severe illness should consider avoiding public places altogether.

In response, the University of Massachusetts Boston on Friday reinstated its indoor mask requirement.

The latest Omicron subvariant that has become dominant, XBB.1.5, is highly transmissible. So as the sheer number of people who get infected rises, even a small percentage of hospitalizations adds up to a lot of people.

“It’s pretty consistent: When we see more transmission, we see more adverse outcomes,” said Julia R. Raifman, assistant professor of health law, policy and management at the Boston University School of Public Health. “When there are more cases, there will be more hospitalizations and more death.”

That’s the moment to ramp up mitigation, she said, by making vaccines easy to find and get, and encouraging masking and ventilation.

Scarpino also favors targeted mask mandates when virus-related cases hit certain thresholds, such as the doubling of the number of deaths that occurred over the past month. “The data suggest it’s time for mask mandates,” he said.

Dr. Peter Hotez, co-director of the Center for Vaccine Development at Texas Children’s Hospital and dean of the National School of Tropical Medicine at Baylor College of Medicine, said he believes the latest strains of the virus are breaking through the protections against severe illness.

“My interpretation of the data is that you’re seeing declines in protection against hospitalizations,” Hotez said. He expects a wave of cases that, while not as dramatic as in previous years, is “still going to be substantial.”

“If you’ve not gotten a bivalent booster, I think you’re going to be at risk of hospitalization,” he said.

Not everyone sees it that way.

“More deaths reflect more virus circulating in the community, and more introductions into networks of older folks at most risk,” said William Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health. “We are always actively looking to see whether any particular variants are nastier than others, but right now there’s not enough evidence one way or the other.”

Dr. Dan Barouch, head of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, noted that an ancestor of XBB.1.5 had not caused a surge in severe cases of the disease.

Barouch theorizes that T cells, an important component of the immune system along with antibodies, continue to protect vaccinated or previously infected people from severe illness. His laboratory hopes to release the results of another study soon that he expects will show that XBB.1.5 also evades antibodies but not T cells.

“That’s likely the reason we are not seeing a huge increase in severe disease,” said Barouch.

Hospitals are full, with overcrowded emergency rooms, but “COVID is not the principal driver of the hospital capacity problem,” said Dr. Paul Biddinger, director for emergency preparedness at Mass General Brigham. “The primary driver of all of this is the fact that there is a tremendous need for medical care” and people are very sick with a variety of illnesses.

Jonathan Saltzman and Jessica Bartlett of the Globe staff contributed to this report.

Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her @felicejfreyer.