COVID-19 Vaccines Prevented 279,000 Deaths, Study Finds

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Key Takeaways

  • The quick rollout of COVID-19 vaccines likely prevented 1.25 million hospitalizations and nearly halved the death rate in the first six months of 2021. 
  • The study, published by The Commonwealth Fund and Yale University, uses mathematical modeling to estimate vaccine efficacy. 
  • The vaccines were particularly effective at slowing hospitalizations and deaths and relatively less effective at preventing spread of the virus.

COVID-19 vaccines saved around 279,000 lives and prevented 1.25 million hospitalizations in the United States, according to a new study led by Yale University and the Commonwealth Fund.

Researchers found that without any vaccination program, the number of deaths would have nearly doubled by the end of June 2021. The spread of the highly transmissible Alpha variant in spring of 2021 could have ushered in a surge of 4,500 deaths per day. 

If vaccines had been rolled out at half the actual rate, an additional 121,000 Americans could have died and more than 450,000 more could have been hospitalized.

“This isn't just an abstract thing,” Eric Schneider, MD, MSc, an author of the study and senior vice president for policy and research at the Commonwealth Fund, tells Verywell. ”This is actually affecting the population. Here are the people whose lives were saved as a result of this intervention.”

COVID-19 vaccines prevented 279,000 deaths
COVID-19 vaccines prevented around 279,000 deaths in the U.S.

Source: The Commonwealth Fund

As of July 11, the U.S. has administered over 387 million COVID-19 vaccine doses, with 55.5% of Americans having received at least one dose. Between January and mid-June, the number of cases has fallen from more than 300,000 to less than 20,000 per day.

However, researchers of the study warn that the spread of new viral variants, like Delta, threaten to reverse these gains. 

COVID-19 Vaccines Averted a Spring Surge 

The U.S. recorded roughly 300,000 deaths during the first half of 2021. Rapid vaccination rollout has prevented that number from doubling, according to the researchers.

“That's a big impact for any public health intervention,” Schneider says. “The most we usually hope for is sort of a 10% or 20% reduction, but this is huge in a short time frame.”

Schneider estimates that the surge in deaths in the U.S. would have peaked in April or May when the Alpha variant took hold of the country. It would likely have been larger than any previous waves of outbreaks. Instead, COVID-19 cases declined during much of the spring thanks to the vaccine development and rollout efforts.

Estimated cumulative COVID-19 cases averted by U.S. vaccination program compared to no vaccination program and 50 percent of actual vaccination rate achieved
COVID-19 vaccines prevented about 26 million cases.

Source: The Commonwealth Fund

According to the study, the COVID-19 vaccines prevented about 26 million cases. With a vaccination program at half the pace, some 22 million cases would have been averted. The difference between both these scenarios is relatively little, compared to the estimations for hospitalizations and deaths. The study shows that while the vaccines are highly effective at preventing serious disease, they do not likely totally prevent transmission and mild illness.

“The vaccines may not be completely effective when it comes to preventing infection with these new variants, but they're very effective when it comes to preventing severe outcomes,” Joshua Cohen, PhD, deputy director of the Center for the Evaluation of Value and Risk in Health at the Institute for Clinical Research and Health Policy Studies at Tufts Medical Center, tells Verywell.

What This Means For You

The report underscores how effective the vaccines are at preventing serious illness and death. If you are unvaccinated, you can find more information about how they work and where to schedule an appointment at

Building a Reliable Model

The researchers accumulated data from various sources including the Centers for Disease Control and Prevention (CDC) and published scientific papers.

To run a simulated model, they factored in the U.S. demographics, how different age groups experienced cases and hospitalizations, the relative transmissibility of each variant, how long it took infected people to become contagious, and more.

Researchers had to train and run the model to see how well it reflected reality over a period of time. Once it was proven reliable, they tested different scenarios, like how changes in the vaccination rate affected the number of cases and hospitalizations. 

While the model considers a wide array of factors that drive COVID-19 health outcomes, Schneider says it can be challenging to account for how people actually act.  

“You could probably walk around any American city right now and see different parts of the city, behaving in different ways, and that can be hard to capture accurately in a model," he says.

Implications for the Future

Models like this one put into perspective the true value of public health interventions like vaccination. Cohen says he hopes that by demonstrating how much loss and chaos was prevented, government officials will feel incentivized to keep ramping up vaccination efforts.

“By looking at how our actions have affected outcomes so far, it can help us understand the benefits of vaccination going forward,” Cohen says. 

Schneider says that having a better understanding of how the vaccine program blunted a potential wave spurred by the Alpha variant could help health experts and policymakers navigate the increased spread of the highly contagious Delta variant. 

“If we can produce the same effect against Delta by vaccinating the remaining unvaccinated people, that's going to be very powerful,” Schneider says.

The model could also be useful in showing how the differences in states’ vaccination rates impact health outcomes. More than 70% of people have been vaccinated in some states, while vaccination rates remained below 30% in about 1,000 U.S. counties as of July 1, CDC director Rochelle Walensky said last week.

Publishing data on the success of vaccines while the world is still in the midst of the pandemic could help guide prevention efforts in upcoming months and years. The authors say they hope the findings will encourage people to get vaccinated.

“It's very hard to roll out prevention programs and for people to take them seriously because people aren't aware of the deaths that didn't occur, or the cancers that didn't happen or the car crashes in which people's lives were saved,” Schneider says. “We tend to see the deaths and illnesses and cancers and forget that we actually have some agency and some control.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Commonwealth Fund. Deaths and hospitalizations averted by rapid U.S. vaccination rollout.

  2. Centers for Disease Control and Prevention. COVID data tracker.

  3. Centers for Disease Control and Prevention. Trends in number of COVID-19 cases and deaths in the US reported to CDC, by state/territory.

By Claire Bugos
Claire Bugos is a health and science reporter and writer and a 2020 National Association of Science Writers travel fellow.