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Why Omicron Is More Contagious, But Less Threatening, Than Delta

January 04, 2022

Emergency departments are full across the country, but the most serious impact from the COVID-19 virus is still being caused by the Delta variant, not the newer Omicron variant.

That, according to recently released research, might be because the Omicron variant, while viewed as much more contagious and a threat to even those who have been vaccinated, is not attacking tissue in patients’ lungs as aggressively. That suggests most infections will not usually be as serious or life-threatening.

The information is new, however, and experts need to monitor more cases and process the data to be certain. Each variant of the coronavirus behaves differently in the human body, and in different age groups.

“Animal studies are showing that, but we need to sort it out,” said Dr. Ulysses Wu, Hartford HealthCare’s System Director of Infection Disease and Chief Epidemiologist, of the research. “Omicron is less likely to replicate in the lungs so that may be why it’s less serious, but we need more information.”

The research was first revealed by White House Chief Medical Advisor Dr. Anthony Fauci, who relayed details from a Chinese study to the media.

“Hamster models show that Omicron poorly infects and spreads in the lung, and is less pathogenic compared to Delta in a hamster model,” Dr. Fauci said. “Belgian researchers in Syrian hamsters (are seeing) the same thing.”

Other ongoing studies funded by the National Institutes of Health (NIH) probing the same subject are being conducted at the NIH Vaccine Research Center, he added. One question is why the variant seems to be affecting more young people than others.

Both Drs. Fauci and Wu stressed that the information does not mean people should become more complacent about protecting themselves and others from the virus.

In a media briefing, Dr. Wu said medical professionals worldwide are watching the interaction between the Delta and Omicron variants and how it’s affecting the way people interact and when or if they go to the hospital for medical attention.

At Hartford HealthCare, the number of hospitalized patients has almost reached the peak of the first wave of the pandemic in 2020 – with 419 people hospitalized Jan. 4 – but only a fraction are critically ill. Dr. Ajay Kumar, Hartford HealthCare’s Chief Clinical Officer, said at the highest point 128 patients were in the system’s intensive care units. On Jan. 4, there were 55.

“These are still predominantly people with Delta who are unvaccinated,” he said.