Researchers analyzed electronic health records for about 80,000 children under the age of 5 who were infected with Covid-19 for the first time in the United States.
They found that the Omicron coronavirus variant is “inherently milder” among children under 5, with infection leading to “significantly less severe outcomes” than the Delta variant, according to a preprint study published Thursday.
The study also showed about 70% reduction in hospitalizations, intensive care unit admissions and mechanical ventilation among children infected with Omicron compared with those infected with Delta. They also found a 29% reduction in visits to the emergency room. Data on deaths was not included, as there were so few reported.
About 1% of children infected with Omicron were hospitalized, compared with about 3% of children with Delta.
The study also found that both variants disproportionately infected Black children, but especially the Omicron variant. More than a quarter (26%) of the children infected with Omicron were Black, but less than 15% of the children who had any encounter with the health care system during the same timeframe were Black.
“Despite this encouraging result, further studies are needed to monitor the longer-term acute consequences from Omicron infection, the propensity for development of ‘long COVID,’ the rapidity of spread, potential for mutation, and how prior infections alter clinical responses,” the researchers wrote.
“Additionally, although infections from the Omicron variant, based on this analysis, appear to be milder, because of Omicron’s increased transmissibility, the overall number of emergency department visits, hospitalizations, ICU admissions, and mechanical ventilator use in children may still be greater with the Omicron variant than the Delta variant," they continued.
Covid-19 hospitalizations among children have reached record highs in recent weeks. In the last week of December, there were about 10 hospitalizations for every 100,000 children under the age of 5, according to data from the US Centers for Disease Control and Prevention.
More on the study: The study included about 7,000 children infected during a time when the Omicron variant was predominant and about 63,000 children infected when the Delta variant was predominant. Virus samples were not sequenced for each individual child, but were instead assumed based on broader sequencing data from the time. Omicron accounted for about 92% of samples during the two weeks ending January 6, while Delta accounted for 99% of samples between September and mid-November.