(Reuters Health) - The Omicron variant was linked with "substantial" excess mortality in Massachusetts, far greater than the preceding Delta wave, researchers say.
During the 23 weeks in 2021 when Delta was predominant, Massachusetts saw 1,975 more deaths from all causes than would be expected during that period based on historical data, whereas there were 2,294 excess deaths during the first eight weeks of the Omicron period, researchers report in JAMA.
The per-week Omicron to Delta incident rate ratio for excess mortality was 3.34, they calculated.
"We saw excess mortality in every adult age group," said study leader Dr. Jeremy Samuel Faust of Brigham and Women's Hospital and Harvard Medical School in Boston.
The study cannot prove that all the excess deaths were from COVID-19. All-cause excess mortality statistics "just say what's happening on the ground," Faust said. "If there's a huge spike parallel to a COVID outbreak, you make the inference"
Pressure on health care systems during the brief but intense Omicron wave in January and February 2022 may have contributed to the increase, but he does not think it played a big part.
The finding that Omicron was worse for Massachusetts also reflects the fact that the state's excess mortality rate during the Delta period was relatively low, Faust said. States with relatively high excess death rates during the Delta period might not notice a difference with Omicron.
"People want to believe Omicron is milder," he added, but multiplying the Omicron's lower rate of deaths by its far higher rate of infection would explain the higher excess mortality his team found.
Massachusetts has "a highly immune population" due to vaccination or natural infection, Faust said. "In this context," he added, the higher excess mortality "is nothing to shrug off."
SOURCE: https://bit.ly/3lsD78q JAMA, online May 20, 2022.
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