Is Omicron really less severe than Delta? Here's what the science says.

Is Omicron really less severe than Delta? Here's what the science says. This variant is more transmissible. So how do you protect yourself? And what are the implications for vaccines, masks, hygiene, and social distancing? Science

If you get COVID-19 in the United States right now, chances are high that it’s the Omicron variant, which now accounts for around 95 percent of the country’s reported cases. With dozens of mutations, Omicron is different from the previously dominant Delta variant in significant ways, which means that, after two years of getting a handle on how to manage risk, you might need to shift at least some of your behaviors.

Among the changes, Omicron is more transmissible and better at evading existing antibodies. “To me, the biggest shift, the most shocking thing, is how incredibly infectious this thing is. I have never seen anything so infectious in my life,” says Carlos del Rio, an epidemiologist and infectious diseases specialist Emory University in Atlanta, Georgia. At the same time, Omicron causes different symptoms and seems to lead to less severe disease.

Still, different strains of SARS-CoV-2 share important similarities, and much of the basic public health advice—get vaccinated, wear a mask—remains the same. Here’s what the latest research says about staying safe in the age of Omicron.

Is Omicron really causing less severe disease than Delta?

Multiple lines of evidence from various parts of the world suggest that the Omicron variant causes a less severe form of COVID-19. In South Africa, where Omicron was first detected in November 2021, a private health insurance administrator reported in mid-December that adults with Omicron were 29 percent less likely to be hospitalized, compared with adults infected several months earlier. In the U.K., the rate of hospital admission among people who went to the emergency room with Omicron was a third of what it was for Delta, according to a summary of research from the U.K. Health Security Agency released on December 31, 2021.

As of early January, U.S. adults with Omicron were less than half as likely to visit the emergency room, be hospitalized, or be put on a ventilator, according to preliminary work by researchers from Case Western Reserve University School of Medicine. Their study, which has not yet been peer-reviewed, examines data for more than 14,000 patients and accounts for their vaccination status and any pre-existing conditions.

A shift in symptoms reflects those trends, del Rio says. In the hospital, patients are showing up less often with pneumonia-like symptoms and hyperactive immune systems, as seen in previous waves. Instead, they’re more often presenting with congestion and scratchy throats. “In Omicron, the symptoms are more like a head cold,” he says.

Does severity differ based on age or preexisting conditions?

Omicron appears to be less severe than Delta in all age groups, even in adults older than 65 and in children too young to be vaccinated, according to the Case Western study. Still, as with other health issues, age remains a factor, del Rio says. “For any disease, if you're older, you're going to do a lot worse,” he says.

People with underlying conditions or compromised immune systems also remain more vulnerable, as do people who are unvaccinated. Although current vaccines are less effective at preventing symptoms from Omicron than from Delta, the U.K. report found that people who were fully boosted were up to 88 percent less likely to be hospitalized with Omicron compared with unvaccinated people. Hospitals around the country report that unvaccinated patients make up the majority of people now in intensive care units.

Regardless of age or health status, people infected with Omicron can feel terrible even if they don’t have to go to the hospital, and the variant continues to hospitalize and kill many people, emphasized Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, in a virtual press conference last week.

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