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Omicron gives new meaning to calculated risk

Forty-odd years ago, Stanford engineering professor Ron Howard coined the term ‘micromort’ to quantify a 1-in-a million chance of death.

Heather Hopp-Bruce/Globe Staff; rawpixel/afxhome/Adobe

For two years, we have been living with the risk of a coronavirus infection, and the attendant chances, in declining order of possibility, of illness, hospitalization, and death.

But there have been almost no reliable tools to help us navigate these risks. It wasn’t so long ago that friends of mine were sanitizing their mail and triple-masking outdoors — precautions later revealed to be excessive, but who knew at the time?

There is a science of risk. Forty-odd years ago, Stanford engineering professor Ron Howard coined the term “micromort” to quantify a 1-in-a-million chance of death. For example, there were 413 skydiving deaths in the United States between 2000 and 2016, out of over 48 million recorded jumps. So each jump had a risk of roughly 8 micromorts.


For comparison, everyday life has its risks. Once you’ve woken up, there is a 22 micromort, i.e., 0.000022, i.e., a 1-in-50,000 chance that you will expire before day’s end. Flying is safer than driving, and so on.

So what about COVID? Using Centers for Disease Control and Prevention data, Dr. Ethan Craig at the University of Pennsylvania calculated coronavirus risks for May 1 to Oct. 18, 2021. Risk of death among the vaccinated was 0.25 micromorts a day. Risk of death among the unvaccinated came to 6.3 micromorts, roughly 25 times higher. “Does the idea of BASE jumping make you nervous?” Craig wrote. “Being unvaccinated sure should, as well.”

Craig admits that there are inaccuracies built into his “back-of-the-envelope” calculations, and that risks rise for the elderly and the immunocompromised. That said, he is far from alone in trying to quantify Life Under COVID. A group of “relentless tabulators” in San Francisco, including a couple of MIT grads and a physician, wanted to figure out how risky it was to go shopping, take a bike ride, or attend a protest during the pandemic.


As a homage to Howard, they created the “microcovid” metric, a 1-in-a-million chance of catching COVID. Just this week, they updated their online Microcovid Calculator to take account of the teeming Omicron infections. I plugged in the details of my Wednesday lunch with my fully vaccinated friend Roger at the deserted Ani’s Cafe in Belmont. It set my risk at about 50 microcovids, or what they deem to be one-quarter of my weekly COVID “risk budget.” That is, a 1 in 20,000 chance of being infected.

Post-Omicron, Craig has rethought his article, somewhat. In November, he noted that “a vaccinated individual engages in many activities that are associated with a higher risk for death than COVID-19 — including driving to work.” Now, “I suspect some of the numbers will prove to be pretty similar,” he told me. “For an otherwise healthy, fully vaccinated and boosted individual, the risk for an adverse outcome remains low.”

But fast-spreading Omicron has changed the collective risk, he explained. “Your individual risk factors into a population risk, where the chance of spread is much greater now.” Craig has adjusted his personal COVID risk budget accordingly, not eating indoors and not inviting guests to his home.

“We are in a much better place in a lot of ways” now, compared with March 2020, he said. “Now we have vaccines that work remarkably well at preventing severe outcomes (despite an immune-evasive variant). We know who is at highest risk for severe illness. When I go to work, I’m not afraid like I was then. At this point, I’d say I respect the virus, and take it seriously, but don’t fear it.”


Everyone, including Craig, knows there is a lot of coronavirus circulating now. The generally sane Dr. Robert Wachter, chairman of the department of medicine at the University of California at San Francisco, says this month will be “awful” for Omicron spread.

For the immediate future, mundane activities such as shopping or chatting with the postal worker give new meaning to the term “calculated risk.” The best advice: Proceed with caution.

Alex Beam’s column appears regularly in the Globe. Follow him on Twitter @imalexbeamyrnot.