Is Covid-19 more dangerous than driving? How scientists analyze Covid risks

Like it or not, the choose-your-own-adventure phase of the pandemic is upon us.

Mask requirements have fallen. Some free trial sites have been closed. Those parts of the United States that were still trying to collectively quell the pandemic have largely shifted their focus from community-wide deliberation.

Now, even as case numbers rise again and more infections go unreported, the responsibility rests with individual Americans to decide how much risk they and their neighbors are at risk from the coronavirus — and what, if anything, to do about it.

For many people, the threats of COVID have diminished dramatically over the two years of the pandemic. Vaccines reduce the risk of being hospitalized or dying. Powerful new antiviral pills may help keep vulnerable people from getting worse.

But not all Americans can count on the same protection. Millions of people with compromised immune systems do not fully benefit from vaccines. Two-thirds of Americans and more than a third of those over the age of 65 have not received the critical safety of a booster shot, with the most worrying rates being among blacks and Hispanics. And patients who are poorer or live farther from doctors and pharmacies face major hurdles in getting antiviral pills.

These vulnerabilities have made calculating the risks posed by the virus a difficult task. The recent suggestion by federal health officials that most Americans could stop wearing masks because hospital admissions have been low has caused confusion in some quarters about whether there has been a change in the likelihood of infection, scientists said.

“We do a really terrible job of communicating risk,” said Katelyn Jetelina, a public health researcher at the University of Texas Health Science Center at Houston. “I think that’s also why people throw their hands up in the air and say, ‘Fuck it.’ They are desperate for some kind of guidance.”

To fill this gap, scientists are rethinking how COVID risks can be discussed. Some have examined when people could uncloak themselves indoors when the goal was not just to keep hospitals from overcrowding, but also to protect immunocompromised people.

Others are working on tools to compare infection risks to the dangers of a variety of activities, finding, for example, that an average unvaccinated person aged 65 and older is about as likely to die from an omicron infection as someone from 18 months of heroin use .

But how people perceive risk is subjective; No two people feel the same about the likelihood of dying after a year and a half of heroin use (about 3% by one estimate).

Additionally, many scientists said they are also concerned that this latest phase of the pandemic is putting too much strain on individuals to make decisions about how to protect themselves and others, especially while tools to fight COVID have remained beyond the reach of some Americans.

“As much as we don’t want to believe it,” said Anne Sosin, who studies health justice at Dartmouth College, “we still need a society-wide approach to the pandemic, particularly to protect those who cannot fully benefit from vaccination.”

The coronavirus is new enough and its long-term effects so unpredictable that measuring the threat of infection is a thorny issue. (Source: The New York Times)

Collective Metrics

While COVID is far from America’s only health threat, it remains one of the most significant. In March, even as deaths from the first omicron surge plummeted, the virus was still the third leading cause of death in the United States, behind only heart disease and cancer.

Overall, more Americans have died than in normal times, a sign of the virus’ heavy toll. At the end of February, 7% more Americans were dying than would have been expected based on previous years – a contrast to Western European countries like the UK, where the total number of deaths recently has been lower than expected.

How many viruses are circulating in the population is one of the most important measures for people trying to assess their risks, scientists said. That remains true even though case numbers now far underestimate true infections because so many Americans are testing at home or not testing at all, they said.

Even as many cases are missed, the Centers for Disease Control and Prevention is now putting most of the Northeast at “high” levels of virus transmission. In parts of the Region, case numbers, while far lower than winter, are approaching the highs of the fall delta variant rise.

Much of the rest of the country has what the CDC calls “moderate” transmission rates.

Estimation of the Covid risk (Source: The New York Times)

COVID versus driving

Even two years into the pandemic, the coronavirus remains new enough and its long-term effects unpredictable enough that measuring the threat of infection is a thorny issue, scientists said.

An unknown number of those infected will long develop COVID, leaving them severely weakened. And the risk of catching COVID extends to others, possibly in poor health, who may consequently be exposed.

Still, some public health researchers have tried to make risk calculations more accessible by comparing the virus to everyday dangers as the population had far more immunity than they used to.

In the United States, the comparisons are particularly tricky: The country doesn’t conduct the random swab studies needed to estimate infection numbers, making it difficult to know what proportion of those infected die.

Cameron Byerley, an assistant professor of mathematics education at the University of Georgia, has developed an online tool called COVID-Taser that allows people to adjust their age, vaccination status and health background to predict the risks of the virus. Her team used estimates from earlier times of the pandemic of the proportion of infections that led to poor outcomes.

Her research showed that people have trouble interpreting percentages, Byerley said. She recalled that her 69-year-old mother-in-law was unsure about worrying earlier in the pandemic after a news program said people her age had a 10 per cent risk of dying from an infection.

Byerley suggested her mother-in-law imagine if she died once in 10 times she used the toilet on any given day. “Oh, 10% is terrible,” she recalled as her mother-in-law said.

For example, Byerley’s estimates showed that an average 40-year-old who was vaccinated over six months ago had about the same chance of being hospitalized after being infected as someone who died in a car accident making 170 cross-country journeys. (Newer vaccinations offer better protection than older ones, making these predictions more difficult.)

The risks are higher for immunocompromised people. An unvaccinated 61-year-old with an organ transplant, Byerley estimated, is three times more likely to die from an infection than someone who dies within five years of being diagnosed with stage 1 breast cancer. And that transplant recipient is twice as likely to die from COVID than someone who dies climbing Mount Everest.

Looking at the people most at risk, Dr. Jeremy Faust, an emergency room physician at Brigham and Women’s Hospital in Boston, set out last month to determine how low cases would need to be for people to stop masking indoors without endangering those with extremely compromised immune systems.

He imagined a hypothetical person who does not benefit from vaccines, wears a good mask, takes prophylactic medication that is difficult to obtain, occasionally attends meetings and shops, but does not work personally. He has set himself the goal of keeping the probability of infection of vulnerable people below 1% over a period of four months.

To reach that threshold, the country would need to continue indoor masking until transmission falls below 50 weekly cases per 100,000 people — a stricter limit than the one the CDC currently uses, but one it still says is a benchmark to strive for offers.

“If you just say, ‘We’ll take the masks off when things get better,’ — that’s true, I hope — but it’s not really helpful because people don’t know what ‘better’ means,” Faust said.

This article originally appeared in The New York Times.

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