The omicron variant of SARS-COV-2 caused more “excess deaths” in Massachusetts in eight weeks this year than the delta variant did in 23 weeks when it was the dominant variant. Excess deaths are a measure of how many more deaths occur in a given time period than would normally be predicted for a population.

The excess deaths caused by omicron during the study period occurred despite existing evidence that those who caught that version of COVID-19 tended to have less dangerous outcomes, according to anew study published Friday in the Journal of the American Medical Association.

The study found 2,294 excess deaths in Massachusetts during the omicron surge from late December 2021 to late February of this year — 16% more than the 1,975 deaths reported during the delta variant surge that lasted from June to December of last year. The study attributes the increase in excess deaths to omicron’s high contagiousness.

“The data that we published really slams home an important point for me,” said Jeremy Faust, an emergency physician at Brigham and Women's Hospital, and the lead author of the study, “which is that — even in a state that is highly vaccinated and in which there have been a lot of infections, so people have a lot of immunity — still, a variant that's quote unquote 'milder' can cause this massive amount of increase in mortality.”

Faust said his team’s findings underscored the impact of the omicron variant’s contagiousness.

“This is the idea that, OK, maybe it's a slightly lower fatality rate for every infection,” Faust said, “but you multiply that by a far, far higher number of infections and you get a big number. So if it's half as deadly but ten times as contagious, you have a massive increase in mortality.”

The increase in mortality associated with the omicron variant disproportionally affected residents of color in Massachusetts, said Dr. Cassandra Pierre, an infectious disease physician who is the associate hospital epidemiologist and the medical director of public health programs at Boston Medical Center.

Pierre said, before the omicron surge, the gap in COVID-19 deaths between Black people and white people was closing. But she said that gap widened again during the surge at the start of the year.

“And there may be multiple reasons for that,” said Pierre, “I mean, we do still know that our Black population is under-vaccinated relative to the white population. … I'm certainly sure that the Black population is un-boostered relative to the white population."

She also said racial health disparities and impacts of the ongoing pandemic also contribute.

“I'm talking about the pandemic itself, with the relative isolation, the inability to see a health care provider reliably in person, some people being laid off,” Pierre added. "There was a greater economic toll in Black and brown communities, and hence the lack of health insurance and the ability to even engage in health care that goes along with that.”

Faust said it’s important to note that the study found that excess deaths for both the last omicron surge and the delta surge were up in all age groups in the state. For example, he said, about 300 more residents between the ages of 18 and 49 died than the number who would have if there was no pandemic.

“And I always stop to think that it's sad that because it's not thousands or hundreds of thousands or a million that that seems like not very much,” Faust said, “But actually 300 deaths among adults 18 to 49 in a state that has about one-fiftieth of the population of the country, you start doing the math and you realize that this is every bit as big of a crisis for young adults as … the opioid crisis, HIV/AIDS — it's similarly lethal and we lose track of that.”

Faust expects more excess deaths in the current surge, but he said it’s still unclear right now what the best public health response should be.

“The reality is that people will only listen to our advice and our guidance and our observations once in a while,” said Faust. “And so while I personally am wearing a mask in most situations … you have to decide when to spend your clout.”

“And it's frustrating because we could get to zero deaths right now," he added. "We won't, but maybe that's because we're hoping that in the next big wave we will have more people come along for doing the right thing and saving a lot of lives at once.”