Cleveland study finds omicron causes less severe illness in young children than delta

A new study of COVID-19 patients under the age of 5 found the omicron variant appears to cause less severe disease in this age group, but is more contagious than the delta variant. [Zoia Kostina / Shutterstock]
A new study of COVID-19 patients under the age of 5 found the omicron variant appears to cause less severe disease in this age group, but is more contagious than the delta variant. [Zoia Kostina / Shutterstock]
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The omicron variant of the coronavirus appears to cause less severe illness but is about 15 times more contagious than delta in children under the age of 5, according to a new study from the Case Western Reserve University School of Medicine.

An analysis of 79,000 pediatric COVID-19 cases from across the U.S. found emergency room visits were down 29 percent in the recent omicron surge compared to the delta wave, while the use of ventilation dropped by 71 percent, according to the researchers.

Dr. Pamela Davis, one of the study’s authors and a CWRU community health professor, said the study also found the omicron variant to be significantly more contagious than the delta variant.

While children appear less likely to develop a severe case, the sheer number of new cases has still caused pediatric hospitalizations to rise, she said.

“There are many, many more children getting infected, but of those who get infected, the proportion who get really sick is lower. On the other hand, a lower proportion of a very large number makes for a lot of sick children in the hospital and a lot of challenge to the pediatric health systems,” Davis said.

As Ohio’s COVID-19 case rates began to rise dramatically at the end of December due to the emergence of omicron, Cleveland doctors warned they were seeing an increase in pediatric COVID-19 patients.

In this study, Davis and Rong Xu, a biomedical informatics professor at CWRU, compared similar populations of kids from a national database who had not been previously infected with COVID-19.

One group of kids under 5 contracted COVID-19 during the fall of 2021, when the delta variant was the predominant strain across the U.S., while another group tested positive at the end of December and early January when omicron was driving the majority of cases.

Researchers looked at emergency room visits, hospitalizations, ICU admissions and mechanical ventilation rates in both groups.

Across the board, children infected with the omicron variant reported less severe outcomes, Xu said, but the risk of developing severe disease was had not been completely eliminated.

“The infectious rate … was about 10 to 15 times compared to the delta variant, and the reduction in clinical outcomes was 30 to 70 percent. So, add this together, [and this is] why we see the number of hospitalizations and other clinical outcomes skyrocket,” Xu said.

Follow-up studies are needed on these patients to get a full picture of their outcomes and determine whether they developed long-haul COVID symptoms due to the omicron variant, Xu said.

Many adults who had otherwise mild COVID-19 cases experience concerning long-term symptoms, Davis said, so more research is needed to see how omicron affects the pediatric population.

“I’m kind of worried about the long COVID-19 and the kids,” Xu added. “In this study, we only studied the severe outcomes like hospitalization and ICU visits, but really right now we don’t know what’s the long-term effects of COVID-19 in children, for example in the brain and other body systems.”

Based on the study’s findings, Davis said children under 5 should wear masks in public and adults around them should take precautions, such as wearing masks and getting the vaccine, because this age group cannot yet be vaccinated.

“It’s important to realize that this is not going to be as high a chance of your child winding up in the hospital, but as Dr. Xu said, it is not zero, and there are a number of children who are very, very ill,” Davis said. “Especially if the child [is] immune-compromised, or other factors that would make you concerned about the impact of COVID, boy, you’ve got to take steps to protect that child.”

The study is under peer review and is expected to be published in a medical journal.

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