Covid-19 vaccines saved an estimated 2.5 million lives globally from 2020 to 2024, significantly fewer than earlier estimates that suggested vaccines saved as many as 20 million lives in their first year, a new study has found.

The finding, compiled by Stanford University researchers in collaboration with Italian experts and published in the JAMA Health Forum, calls for a reassessment of vaccine rollout strategies for future pandemics.

“I think early estimates were based on many parameters having values that are incompatible with our current understanding,” lead author and Stanford University epidemiologist Dr. John Ioannidis said. “Aggressive mandates and the zealotry to vaccinate everyone at all cost were probably a bad idea.”

According to the study, 90 percent of the lives saved were among individuals aged 60 or older, with most deaths prevented stemming from vaccinations administered before initial Covid-19 infections. The researchers note that it required about 5,400 doses of the vaccine to avert a single death globally.

Among younger populations, the benefits were far more limited, with fewer than 2,000 lives saved globally among individuals under 30 years old. 

The study pointed out that earlier modeling may have underestimated the number of people already unknowingly infected before vaccination campaigns began and may have overestimated the longevity of vaccine protection. These discrepancies, combined with more conservative assumptions in the new research, resulted in the revised estimate.

While the lower estimate of 2.5 million lives saved is a significant revision from initial projections, the study underscores that COVID-19 vaccines delivered a substantial benefit in limiting global mortality during the pandemic. 

“These estimates are substantially more conservative than previous calculations … but clearly demonstrate an important overall benefit from COVID-19 vaccination over the period 2020-2024,” said professor Stefania Boccia, one of the study’s Italian co-authors.

The study didn’t shy away from discussing the unintended consequences of aggressive vaccine mandates and policies. Dr. Ioannidis observed that employing strategies like lockdowns inadvertently eroded public trust, especially among younger populations and people with lower risk profiles, reducing the overall effectiveness of vaccine campaigns. 

“The coercive, almost messianic messaging caused damage to public health with an increase in vaccine hesitancy and loss of trust in medicine and medical science,” Dr. Ioannidis said.

The study’s findings suggest a need for a more tailored approach to vaccine distribution, focusing primarily on at-risk populations. Dr. Monica Gandhi, an epidemiologist at the University of California, San Francisco, supported this conclusion in an accompanying commentary. 

“Long-shuttered schools in the U.S. were not necessary to protect children and did harm them in terms of learning loss, especially among children from high poverty backgrounds,” Dr. Gandhi said.

The researchers also advocated for rigorous, long-term randomized trials for future vaccines to provide a clearer understanding of their benefits and limitations, ensuring data reliability and public trust.