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Case Western Reserve University study finds omicron variant of COVID-19 to be milder than delta variant

COVID-19 omicron
Posted at 4:04 PM, Jan 07, 2022

CLEVELAND — Researchers at Case Western Reserve University in Cleveland have determined during a study that the newest variant of the COVID-19 virus, omicron, is milder than the previous variant, delta, and that the outcomes of contracting the omicron variant have proven to be "significantly less severe."

Dr. Pam Davis—The Arline H. and Curtis F. Garvin research professor, School of Medicine—and Dr. Rong Xu—Professor of Biomedical Informatics, director, Center for AI in Drug Discovery, School of Medicine—led the study, analyzing data from patients who contracted COVID-19 between September and December of 2021.

The study is the first on omicron to be completed in the U.S. and has in the process of being peer-reviewed for publication in a journal.

The pair had been working together for a year and a half, using a database to find out how COVID-19 affects people with other diseases.

"This database is 85 million people from 63 different health systems across the country. So it's a very diverse group," Davis said.

The data collected for this particular study included more than 14,000 patients who were infected with the omicron variant at the end of December. It was then compared to data collected from those who had been infected with the delta variant earlier in the fall, trying to determine "are the outcomes better, are the outcomes worse? Are the outcomes the same as we've been seeing with delta?” Davis explained.

In their findings, Davis and Xu showed that first-time omicron variant infections were associated with significantly less severe outcomes in comparison to first-time infections of the delta variant.

Those less significant outcomes included lower risk of hospitalization, ICU admission, ventilation needs and emergency room visits within the first three days of infection, the study showed.

Researchers chose the three-day initial window after coming to the conclusion that hospitalizations were on average documented within two days of a positive test for the delta variant and one day of a positive test for the omicron variant.

The study found similar findings as did others in South Africa, Scotland and England. It is among the first to show evidence of reduced severity after infections from omicron than in the delta variant.

While the study found evidence of reduced hospitalizations, ventilation needs and ICU admissions, it did not report comparisons of mortality because so few deaths occurred in the three-day window for either variant and the study requires longer follow-up times to report mortality risk information.

The study also indicated that while infections from the omicron variant were determined to be milder, the number of hospitalizations, emergency room visits, ICU admission and ventilator needs may be numerically higher due to the increased transmissibility of the omicron variant compared to the delta variant.

Since Dec. 24, the final day included in the researchers' study, Xu said the number of omicron infections in the database was "10 times more. So we do see a huge increase just in the past 10 days."

She said that would help them continue to examine certain types of patients in greater detail, including those with diabetes, organ transplants, cancer or compromised immune systems.

To learn more about the full study, click here.

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