Is Covid more dangerous than driving? How scientists analyze the risks of Covid.

Cameron Beyrle, an assistant professor of mathematics at the University of Georgia, has built an online tool called Covid-Taser that allows people to adjust age, vaccine status and health to predict the risks of the virus. Her team used earlier estimates in the pandemic of the share of infections that led to poor results.

Her research shows that people have trouble interpreting percentages, Dr. Beyrle said. She recalled that her 69-year-old mother-in-law was unsure whether to worry earlier during the pandemic after a news program said people her age had a 10% risk of dying from an infection.

Dr. Beyrle suggested to her mother-in-law that if she died once every 10 times when she used the toilet on a given day. “Oh, 10 percent is awful,” she recalls, speaking to her mother-in-law.

Dr. Beyrle’s estimates show, for example, that an average 40-year-old vaccinated more than six months ago faces about the same chance of being hospitalized after an infection as someone dying in a car crash on 170 cross-country roads. travel. (More recent vaccines provide better protection than older ones, which complicates these predictions.)

In immunocompromised people, the risks are higher. An unvaccinated 61-year-old with an organ transplant, according to Dr. Beyrle, is three times more likely to die after an infection than someone to die within five years of being diagnosed with early-stage breast cancer. And this transplant recipient is twice as likely to die from Covid than someone to die while climbing Mount Everest.

With the most vulnerable people in mind, Dr. Jeremy Faust, an emergency physician at Brigham and Women’s Hospital in Boston, worked last month to determine how low cases will have to fall for people to stop masking indoors without compromising those with extremely weakened immune systems.

He imagined a hypothetical man who did not benefit from vaccines, wore a good mask, took hard-to-reach prophylactics, attended occasional gatherings, and shopped, but did not work in person. It seeks to keep the chances of vulnerable people being infected below 1% over a four-month period.