Hospitalizations of young children with the virus surged during the U.S. Omicron wave.
Babies and children younger than age 5 were hospitalized with coronavirus at much higher rates during the latest U.S. surge, when the highly transmissible Omicron variant was dominant, compared with earlier periods in the pandemic, according to the Centers for Disease Control and Prevention.
Hospitalizations of these children were about five times higher during the Omicron surge, between Dec. 19 and Feb. 19, than during the period when the Delta variant was dominant, between June 27 and Dec. 18.
Rates of admission to intensive care also rose dramatically among young children, reaching a peak on Jan. 8 of this year.
Children of color younger than age 5 wound up in hospitals at disproportionate rates. Only one-third of the children were white, while 28 percent were Hispanic and 23 percent were Black. Hispanic people represent just 18 percent of the population, and Black Americans make up 13 percent.
(Six percent of these hospitalizations were among Asian or other Pacific Islander children, about the same as their representation in the population.)
Experts say children of color are infected at higher rates because they are more likely to have parents who work in public-facing jobs, and more likely to live in poverty and in multigenerational households.
Though hospitalization rates for young children are still relatively low, compared to the rates among older Americans, the virus poses special risks to the youngest children and especially to babies.
Infants six months old and younger were the most vulnerable, representing nearly half of the hospitalizations among young children during the Omicron period. They were hospitalized at rates about six times as high at the peak of the Omicron surge, compared with the peak of the Delta wave. Two infants died, the C.D.C. found.
“People should know there are risks to children under 1 that are pretty serious, especially during surges, and they might want to take extra precautions to reduce exposure,” said Julia Raifman, an assistant professor of health law, policy and management at Boston University School of Public Health, who was not involved in the research.
More than 1,000 children younger than age 18 have died of Covid since the pandemic started, including 350 children under 5. But experts also worry about the long-term effects, as well as multisystem inflammatory syndrome, a rare but serious condition.
The C.D.C. study found that most of the children and babies who were hospitalized — about two-thirds — were healthy and did not have underlying medical conditions, as has been the case throughout the pandemic.
No Covid vaccines are currently authorized in the United States for children younger than 5, and the regulatory process has been fraught with delays and setbacks. Public health experts strongly recommend that anyone who comes into regular contact with young children get vaccinated.
“To help protect children too young to be vaccinated, everyone ages five and older, including pregnant women, family members and caregivers, should stay up to date with Covid-19 vaccines,” Dr. Kristin J. Marks, the study’s first author and an epidemic intelligence service officer with the CDC, said in an email.
The study, published on March 15, examined hospitalizations of children in counties in 14 states whose catchment areas represent about 10 percent of the U.S. population.