Hospitalization rates for unvaccinated children ages 5 to 11 were twice as high as among those who were vaccinated during the record COVID-19 surge caused by the omicron variant, according to a US study released on Tuesday.

For every 100,000 unvaccinated children in the age group, 19.1 per were hospitalized with COVID-19 between mid-December and late February, compared with 9.2 per 100,000 vaccinated kids, the US Centers for Disease Control and Prevention reported.

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The researchers looked at nearly 400 hospitalizations in 14 states during the period.

It found that among the 397 children who were hospitalized with COVID when omicron was dominant, 87 percent were unvaccinated, one third had no underlying medical conditions, and 19 percent were admitted to an intensive care unit.

The highly contagious omicron variant, which drove coronavirus infections to record levels in the United States in January, fueled an increase in COVID-19 hospitalizations among those under age 18, leading to concerns about the impact on unvaccinated children.

US regulators had authorized the Pfizer/BioNTech COVID-19 vaccine for children aged 5 to 11 years in October, prior to the omicron surge.

Just 28 percent of children in the age group – around 8 million – are fully vaccinated, according to CDC data.

The study also found that peak COVID-19 hospitalization rates among children in the age group were higher during the omicron wave than when delta was the predominant variant.

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