How to Compare COVID Deaths for Vaccinated and Unvaccinated People

How to Compare COVID Deaths for Vaccinated and Unvaccinated People thumbnail

Looking at COVID data from recent months, it might seem that a large proportion of those who died from COVID were vaccinated. It is important to understand the context of these numbers.

The U.S. Centers for Disease Control and Prevention has compiled data from 28 geographically representative state and local health departments that keep track of COVID death rates among people age 12 and older in relation to their vaccination status, including whether or not they got a booster dose, and age group. Each week in March, on average, a reported 644 people in this data set died of COVID. Of them, 261 were vaccinated with either just a primary round of shots–two doses of an mRNA vaccine or a single dose of Johnson & Johnson’s vaccine–or with that primary series and at least one shot of a booster.

These numbers, taken at face value may seem to suggest that vaccination doesn’t make much of a significant difference. This perception is known as the base-rate fallacy. It is also important to consider the numerator of the fraction, which is the size of the unvaccinated and vaccinated populations. The majority of the U.S. population is vaccinated. Even if COVID is fatal in a small percentage of those who have been vaccinated, it is still a significant problem.

Graphic shows weekly average of ~38 million people age 12  were unvaccinated and ~127 million were vaccinated in March 2022.
Credit: Amanda Montanez; Source: Centers for Disease Control and Prevention

In order to avoid the pitfalls of absolute numbers, it is useful to instead look at incidence rates–usually expressed as the number of deaths per 100,000 people. A very different picture can be obtained by standardizing the denominator for all groups.

Graphic shows average weekly COVID deaths per 100,000 people by vaccination status in March 2022.
Credit: Amanda Montanez; Source: Centers for Disease Control and Prevention

Another way to consider the protection that vaccination provides is to compare death rates between the vaccinated as well as the unvaccinated. For the month of March, “unvaccinated people 12 years and older had 17 times the rate of COVID-associated deaths, compared to people vaccinated with a primary series and a booster dose,” says Commissioned Corps of the U.S. Public Health Service commander Heather Scobie, deputy team lead for surveillance and analytics at the CDC’s Epidemiology Task Force. “Unvaccinated people had an eight-fold higher rate of death than people who had only a primary series,” which suggests boosters may increase protection.

It is also important to take into account the ages and circumstances of those who are about to die. People 65 and older make up the group that is both the most likely to be vaccinated (and boosted) and the most likely to die of COVID. Because the immune system becomes weaker with age, being older is one of severe COVID risk factors. It is clear that vaccination lowers the risk of death when you break down the age groups. Because immunity to vaccination deteriorates with age and some older people don’t have a strong immune response to the primary series of vaccines, being boosted further reduces that risk.

Graphic shows average weekly COVID deaths per 100,000 people by age group and vaccination status in March 2022.
Credit: Amanda Montanez; Source: Centers for Disease Control and Prevention

Another factor to consider is the shrinking unvaccinated population as the pandemic progresses and a large number of people become ill from COVID. This results in a larger number of unvaccinated people, which leads to an increase in deaths despite a lower death rate among those who have been vaccinated. No vaccine is 100 percent effective, but immunization reduces the risk of dying from COVID substantially.

*Editor’s Note (7/7/22): This sentence was edited after posting to correct the populations described by Heather Scobie.

ABOUT THE AUTHOR(S)

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    Amanda Montanez is an associate graphics editor at Scientific American. Follow Amanda Montanez on Twitter.

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      Tanya Lewis is a senior editor

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