But Covid-19 case rates and hospitalizations among children have reached record highs in recent weeks.

"When you have such huge numbers of infected individuals, even a low likelihood of a severe event -- which is generally the case in children; they generally tolerate the virus much better than adults do -- it stands to reason that you're going to see more kids with rare and potentially serious consequences of the infection," said Dr.

This age group is not yet eligible to be vaccinated, and the researchers note that low rates of prior Covid-19 infection also limit their pre-existing immunity.

The study found about 70% reduction in hospitalizations, ICU admissions and mechanical ventilation among children infected with Omicron compared with those infected with Delta.

Data on deaths was not included, as there were so few reported.

Overall, about 1% of children infected with Omicron were hospitalized, compared with about 3% of children with Delta, according to the study.

It included about 7,000 children infected during a time when the Omicron variant was predominant and about 63,000 children infected when Delta was predominant.

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.

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.