The COVID-19 hospitalization rate was twice as high among unvaccinated children ages 5 to 11 than vaccinated ones during the omicron wave, according to a new study by the Centers for Disease Control and Prevention.

Among the nearly 400 hospitalized children whose data were analyzed, 87% were unvaccinated. While the study found that children with diabetes and obesity were more likely to experience severe COVID-19, the researchers noted that 30% of those who were hospitalized had no underlying conditions. About one in five children admitted to hospitals required treatment in intensive care units.

None of the vaccinated children who were hospitalized needed supplemental oxygen.

Kids 5 to 11 became eligible for vaccination in early November, which meant the earliest ones to roll up their sleeves were getting their second shots just as the omicron subvariant was taking hold in the U.S.

Omicron is more transmissible than earlier variants, including delta, and more resistant to vaccines. A March study by New York State health officials, for example, found that the effectiveness of the Pfizer-BioNTech vaccine in preventing infection in 5- to 11-year-olds fell from 68% to 12% during the omicron wave. Protection against hospitalization dropped from 100% to 48%.

But the CDC scientists say their research underscores the importance of children being vaccinated. 

“Increasing vaccination coverage among children, particularly among racial and ethnic minority groups disproportionately affected by COVID-19, is critical to preventing COVID-19-associated hospitalization and severe outcomes,” their paper said.

Non-Hispanic Black children account for the largest group of unvaccinated kids ages 5 to 11 — 34%.

During the peak of omicron surge, the COVID-19 hospitalization rate among children 5 to 11 was 2.3 times higher than it was during the delta peak. ICU admission rates were 1.7 times higher with omicron than delta, the CDC said.

Twenty-eight percent of 5- to 11-year-olds are fully vaccinated, according to data compiled by The New York Times. That number is as low as 10% in Alabama and 12% in Louisiana and Mississippi.