Clinical health outcomes of omicron “less severe” than delta for pediatric patients

New research from Case Western Reserve University (CWRU) School of Medicine suggests that children younger than 5 infected with the COVID-19 Omicron variant have a lower risk of serious health problems than those infected with the Delta variant.

The study, published Friday in JAMA Pediatrics, is the first large-scale research effort to compare the health outcomes of Omicron to Delta coronavirus infection in children 4 years of age and younger; the age group that cannot yet be vaccinated.

The results show that the Omicron variant is 6 to 8 times more infectious than the Delta variant. Serious clinical outcomes ranged from a 16% lower risk for emergency department visits to an 85% lower risk for mechanical ventilation. And about 1.8% of children infected with Omicron were hospitalized, compared to 3.3% with Delta.

The Case Western Reserve-led team analyzed the electronic health records of more than 651,640 children in the United States who had medical contact with health organizations between 9/2021 and 1/2022, including more than 22,772 children infected with Omicron at end-December and end-January; to over 66,000 children infected when Delta was prevalent in the fall. The study also compared the records of more than 10,000 children just before Omicron was detected in the United States, but when Delta was still predominant.

Children under 5 are not yet eligible for COVID-19 vaccines and have a low rate of previous SARS-CoV-2 infections, which also limits their pre-existing immunity.

The team looked at clinical health outcomes for pediatric patients during a 14-day window after SARS-CoV-2 infection. Among the factors they looked at were emergency room visits, hospitalizations, intensive care unit admissions and use of mechanical ventilation.

Further analysis of demographic data revealed that children infected with Omicron were on average younger – 1.5 years versus 1.7 years – and had fewer comorbidities.

The main finding of our research was that significantly more children were infected with Omicron compared to Delta, but infected children are not as severely affected as children infected with the Delta variant. However, with so many more children infected, our hospitals have been hit over the winter months by an influx of young children. »

Pamela Davis, Arline H. and Curtis F. Garvin Research Professor, Case Western Reserve School of Medicine

“We saw the number of hospitalizations within this age group skyrocket in January of this year because the infection rate of Omicron is approximately 10 to 15 times higher than that of the Delta variant” , said Rong Xu, professor of biomedical informatics and director of the Center for AI in Drug Discovery at the School of Medicine. “Omicron is less severe than Delta, however, the reduction in severity range of clinical outcomes is only 16-85%. Also, because so many unvaccinated children have been infected, the long-term effects of COVID-19 infections on the brain, heart, immune system and other organs of children remain unrecognized and worrisome.”

The CDC recommends that people age 5 and older get a COVID-19 vaccine, and that fully vaccinated people age 12 and older get a booster shot. According to updated CDC guidelines, Americans no longer need to mask indoors in counties with a low or medium “Covid-19 community level.”


Case Western Reserve University

Journal reference:

Wang, L. et al. (2022) Incidence rates and clinical outcomes of SARS-CoV-2 infection with Omicron and Delta variants in children under 5 years of age in the United States. JAMA Pediatrics.


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