Omicron may not cause as much lung damage as the delta variant of the COVID-19 virus, according to new lab studies.

That, plus vaccination, may help explain why patients with omicron are not being hospitalized or dying as often as patients infected with previous variants.

But omicron is still killing an average of 1,200 people each day in the United States, about equal to the peak of the second COVID-19 wave in July and August of 2020.

“If it’s milder compared to delta; delta was horrible,” said Joe Grove, a senior lecturer at the University of Glasgow Centre for Virus Research. “This has not necessarily just turned into the common cold all of a sudden. It is still something that we should be concerned about.”

Plus, experts caution, omicron’s ferocious infectiousness means the less virulent virus can still do a lot of damage, especially among the unvaccinated who are elderly or have preexisting conditions.

Lighter on the lungs

A set of new studies in lab animals and petri dishes found that omicron did not infect lung tissue as much as previous variants. And it didn’t cause as much damage or inflammation when it did.

Omicron had no problem infecting tissues in the nose and throat. A preference for the upper airway might help explain why omicron is so infectious, Grove said.

“It’s going to be more easily coughed or sneezed out and spread more easily,” Grove said. “But I am speculating here.”

The lab results are promising, but what happens in lab animals doesn’t always translate to people, Dr. Mike Diamond, an infectious diseases professor at Washington University School of Medicine, cautioned.

“You might say, ‘Well, maybe it’s less severe,'” he said. “But we don’t fully even know that it’s less severe in humans yet.”

Doctors in South Africa said that omicron patients had not been not as sick when the variant swept through that country. Health officials in the United Kingdom reported similar observations.

But it’s not clear if those cases were milder because of the virus or because people were less susceptible.

“In the U.K. there was a very high vaccination rate,” Diamond noted. “And then in South Africa, a lot of people got infected in the first wave, so they’re naturally immune.”

Some encouraging signs are starting to come in. According to an early study in Ontario, Canada, unvaccinated people infected with omicron were 60% less likely to be hospitalized or die than those infected with delta.

Experts warn, however, that the risk of severe disease may be lower, but the odds of catching omicron are higher. The huge number of people infected cancels out the advantage of the milder virus.

Unvaccinated and hospitalized

That’s why hospitals in parts of the United States are filling up again.

In this wave, most hospitalized patients are unvaccinated, by an overwhelming margin.

In New York City, for example, where COVID-19 is spiking again, unvaccinated patients are being hospitalized at a rate 30 times that of vaccinated patients.

The highest rates of hospitalization are among those over 65.

Even if omicron is milder, “it seems to be still doing quite a bit of damage in unvaccinated people,” said University of Texas Medical Branch virologist Vineet Menachery.

“The good news is that there does seem to be a trend that this virus is less severe than previous waves, especially if you’re vaccinated,” he said. For those who got their shots, “the threat of severe disease is probably off the table for most people.”

“On the other hand, for people who are not vaccinated, I think the threat is just as big as it was in March of 2020,” Menachery added. 
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