Between 2020 and 2024, COVID-19 vaccines saved an estimated 2.5 million lives worldwide—equivalent to preventing one death for every 5,400 doses given.
A landmark global analysis led by researchers from Università Cattolica and Stanford University reveals that most lives were saved when people were vaccinated before infection, with the largest impact during the Omicron wave and among those aged 60 and over. The team also calculated 14.8 million years of life gained, underscoring vaccines’ immense contribution to protecting the most vulnerable, even with more conservative estimates than earlier studies.
Global Vaccine Impact: Millions of Lives Saved
Between 2020 and 2024, COVID-19 vaccinations are estimated to have prevented 2.533 million deaths worldwide. That means, on average, one life was saved for every 5,400 vaccine doses given. Most of these lives, about 82 percent, were saved when individuals were vaccinated before encountering the virus. The study found that 57 percent of these prevented deaths occurred during the Omicron phase, and 90 percent involved people aged 60 or older. In total, vaccines preserved approximately 14.8 million years of life (equivalent to one year of life saved for every 900 doses administered).
Behind the Breakthrough: The Research Team and Their Global Collaboration
These findings come from a groundbreaking study published in JAMA Health Forum, led by Professor Stefania Boccia, Professor of General and Applied Hygiene at Università Cattolica. She worked alongside Dr. Angelo Maria Pezzullo, a researcher in General and Applied Hygiene, and Dr. Antonio Cristiano, a medical resident in Hygiene and Preventive Medicine. Dr. Pezzullo and Dr. Cristiano also spent time at Stanford University, collaborating with Professor John P.A. Ioannidis, who directs the Meta-Research Innovation Center (METRICS).
Their work was part of the “European network staff eXchange for integrAting precision health in the health Care sysTems–ExACT” project, funded by the European Research Excellence Program RISE project–Marie Sklodowska-Curie and coordinated by Professor Boccia.
A Comprehensive and Unique Study
Professor Boccia and Dr. Pezzullo explain: “Before ours, several studies tried to estimate lives saved by vaccines with different models and in different periods or parts of the world, but this one is the most comprehensive because it is based on worldwide data, it also covers the Omicron period, it also calculates the number of years of life that was saved, and it is based on fewer assumptions about the pandemic trend.”
How the Analysis Was Done
The experts studied worldwide population data, applying a series of statistical methods to figure out who among the people who became ill with COVID did either before or after getting vaccinated, before or after Omicron period, and how many of them died (and at what age). “We compared this data with the estimated data modeled in the absence of COVID vaccination and were then able to calculate the numbers of people who were saved by COVID vaccines and the years of life gained as a result of them,” Dr. Pezzullo explains.
Elderly Benefited Most; Young Least
It also turned out that most of the saved years of life (76%) involved people over 60 years of age, but residents in long-term care facilities contributed only with 2% of the total number. Children and adolescents (0.01% of lives saved and 0.1% of life years saved) and young adults aged 20-29 (0.07% of lives saved and 0.3% of life years saved) contributed very little to the total benefit.
