Analysis: In a highly vaccinated state, COVID-19 is not increasing mortality

In a new analysis, investigators at the Yale Center for Outcomes Research and Evaluation (CORE) and Harvard indicate that in Massachusetts, a state with a high vaccination rate, the most recent wave of SARS-CoV-2 infection was not associated with an increase in mortality.

The analysis, published in the journal The Lancet Infectious Diseases, is based on data vaccination and hospital data from Massachusetts, where about 80% of its 6.9 million residents are fully vaccinated.

Since March 2022, the researchers said, the reported number of deaths in Massachusetts during the spring — when there was a wave of COVID-19 infections, due primarily to omicron variants of the virus — was not higher than what would have been expected in pre-pandemic times. This was in contrast to prior waves of infection, when there were many excess deaths — that is, higher mortality rates than expected, based on historic norms.

The researchers said the “uncoupling” of new COVID-19 cases from rates of excess mortality — the difference between the observed number of deaths due to all causes during a specific time period compared with the expected number of deaths — was the key finding.

“The findings suggest that the mortality toll of the omicron variant of SARS-CoV-2 was neutralized in a state where vaccination is widespread, further strengthening the case for sensible public health tactics,” said Dr. Harlan M. Krumholz, senior author of the report, director of CORE, and the Harold H. Hines Jr. Professor of Medicine at Yale School of Medicine.

Dr. Jeremy Faust, emergency physician at Brigham and Women’s Hospital at Harvard Medical School, was lead author of the analysis. Co-authors were Chengan Du, Chenxue Liang, Shu-Xia Li, and Zhenqiu Lin, all of CORE; Benjamin Renton of Ariadne Labs and Brigham and Women’s Hospital at Harvard Medical School; and Alexander Junxiang Chen of Harvard.