Vaccines have prevented more than 2.5 million deaths caused by SARS-CoV-2, the virus behind COVID-19, according to a new study. Led by researchers from the Catholic University of the Sacred Heart in Italy, the study found that one COVID-related death was avoided for every 5,400 vaccine doses administered.

About 82% of the lives saved involved people who were vaccinated before contracting the virus. Additionally, 57% of the total lives saved were during the Omicron period, and 90% of the deaths prevented were among individuals aged 60 and above. Overall, the study estimated that vaccines saved 14.8 million years of life globally—equivalent to one year of life saved for every 900 doses administered.

The findings were published in the JAMA Health Forum journal. While previous studies attempted to estimate lives saved by vaccines using different models, timeframes, or regional data, this study is the most comprehensive to date. It uses global data, including the Omicron period, quantifies life years saved, and is based on fewer assumptions regarding pandemic trends.