Covid vaccines averted 3 million deaths in U.S., according to new study

This Wednesday will mark two years since nurse Sandra Lindsay became the first person in the U.S. to receive a Covid-19 vaccine outside of a clinical trial. A study released Tuesday by the Commonwealth Fund shows that in those two years, the Covid vaccines have averted over 3 million deaths in the U.S.

The Centers for Disease Control and Prevention estimates that more than 1 million Americans have died from Covid-19 since the onset of the pandemic. But the study results show the toll would have been even worse had the U.S. had relied upon so-called natural immunity acquired through infection as the only immunological defense against the virus. Without vaccines, the country would have experienced four times as many deaths, 1.5 times more infections, and 3.8 times more hospitalizations in the time since December of 2020. The vaccines also saved the U.S. $1 trillion in additional medical costs.

The study’s key message is that vaccines are “worth our money as taxpayers,” said Isaac Chun-Hai Fung, an associate professor of epidemiology at Georgia Southern University, who was not involved in the study. “We pay for the vaccination campaign and it works. It saves us money and it saves lives.”

Rather than modeling population-level effects, the team of researchers from the University of Maryland, York University, and the Yale School of Public Health used a computational model that allowed them to incorporate factors like waning immunity or different age groups’ eligibility for vaccines and boosters into their calculations. Fung noted that adding all of these parameters together creates more statistical uncertainty in the data, meaning that there’s a larger margin for error in the study’s final results. The authors acknowledge this uncertainty by providing “credible intervals” for their calculations — ranges that show, for example, that their estimates for the number of averted deaths would be between 3.1 million and 3.4 million.

To calibrate their model, the researchers first made sure it could correctly predict actual case, hospitalization, and death patterns for the December 2020-November 2022 time frame. They then removed the vaccination elements of the model to examine what would have happened without the Covid-19 vaccines.

“I was struck by just how many lives were saved,” said Alison Galvani, director of Yale’s Center for Infectious Disease Modeling and Analysis and lead author of the study. “If you look at the time frame since the last two years, when the vaccination period was initiated, the vaccine has saved many more lives than have been lost from Covid.”

The study affirms that the vaccines are most effective against severe illness and death, as hospitalizations were much more affected by vaccination than infections.

A previous version of the study was released in April 2022 and subsequently published in the Journal of Global Health. The December 2022 update added the prevalence of comorbidities in the U.S. population to the model. Other factors the model accounted for included the waning of infection-acquired or vaccine-acquired immunity; boosters characteristics of several variants; the rollout of vaccines to different age groups; and changes in pandemic restrictions and mobility patterns.

The study is one in a series funded by the Commonwealth Fund, which included an earlier study on how a children’s booster campaign could reduce school absenteeism.

Fung said the new study’s results show how to protect people’s health while minimizing interruptions to their lives. That’s an important message for politicians, and also applies to other infectious diseases like the flu, Fung said. “We should continue to support preventive medicine,” he said, “not just Covid-19 vaccinations, but other kinds of vaccines, because it’s keeping people healthy, they can go to work, [which keeps] the economy running.”