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How do we quantify the risk of a COVID infection?

Many things have changed in the two years since the beginning of the COVID-19 pandemic: a series of innovative vaccines have been developed and distributed to a large number of people, highly efficient antiviral treatments are now available (although mostly in richer countries). And, with the fulminant passage of the highly contagious yet less severe Omicron variant through most of the world, there is currently a massive amount of natural immunity among most of the globe’s population.

With restrictions such as mask wearing or social distancing eased or even dropped completely in many countries, more responsibility in calculating the risks of coronavirus infections now lie on the shoulders of each individual. 

Several scientists – such as Katelyn Jetelina (a professor of Epidemiology at the University of Texas School of Public Health) or Cameron Byerley (an associate professor of Mathematics Education at the University of Georgia) – have recently tried to quantify individual risks engendered by COVID, depending upon factors such as age, vaccination status, or comorbidities. “We’re doing a really terrible job of communicating risk,” said Dr. Jetelina. “I think that’s also why people are throwing their hands up in the air and saying, ‘Screw it.’ They’re desperate for some sort of guidance.”

Comparing the risks of being hospitalized or dying from a COVID infection with the risks entailed by engaging in other activities such as driving, participating in wars, or taking drugs, these experts came up with rather optimistic and reassuring statistics. For instance, while an average 40-year-old vaccinated more than six months ago faces the same chance of being hospitalized after an infection as someone does of dying in a car accident in the course of 170 cross-country road trips, an average unvaccinated 65 years old person is as likely to die from an Omicron infection as a person using heroin for one year and a half. However, an average vaccinated and boosted senior 65 or older faces a risk of dying from COVID only slightly higher than that of a soldier fighting for a year in the Afghanistan war from 2011.

While such statistical and probabilistic analyses are indeed reassuring, the fact that the coronavirus is still circulating widely in many areas of the world, while a large number of immunocompromised individuals cannot much rely on vaccines or previous infections to protect them, placing the burden of risk assessment completely on the shoulders of individuals is perhaps not yet the best course of action.

“As much as we wouldn’t like to believe it, we still need a society-wide approach to the pandemic, especially to protect those who can’t benefit fully from vaccination,” said Anne Sosin, an expert in Health Equity at Dartmouth College.

An in-depth discussion of COVID risks, together with comparisons with other activities, can be found in Dr. Jetelina’s open-access article “Understanding Risk,” while Dr. Byerley’s interactive online tool which allows people to adjust their age, vaccination status, or health background in order to predict the risks a coronavirus infection might entail can be accessed here.

By Andrei Ionescu, Staff Writer

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