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Less than 2% of U.S. COVID-19 coronavirus cases have been in children, with infants more likely to be hospitalized than older children, researchers found.

From February 12 to April 2, individuals under age 18 accounted for 1.7% of the nearly 150,000 overall U.S. COVID-19 cases with data on age -- far fewer than might be expected from their representation in the population as a whole (24%), reported Lucy McNamara, PhD, of the CDC's COVID-19 Response Team, and colleagues in an .

Fewer children reported "typical" symptoms of fever, cough, or shortness of breath compared to adults, the analysis also found.

As well, hospitalization rates among children were much lower than in adults, though hospitalization was more common among both infants and children with underlying conditions, such as asthma.

The findings are similar to data from China, which indicated more severe COVID-19 cases, or those requiring hospitalization, tended to be in younger children, and prevalence decreased as children got older.

McNamara and colleagues examined data from 2,572 cases of COVID-19 in children. They noted data on symptoms, underlying conditions, and hospitalization status was only available for a minority of patients.

Of the pediatric cases, over half were from New York, 15% from New Jersey, and just under 30% from other jurisdictions. They added the first pediatric U.S. case was reported to CDC on March 2.

Median age of patients was 11, and nearly a third of cases occurred in teens ages 15-17, with 27% of cases among children ages 10-14, and 15% apiece among children ages 5 to 9, and infants younger than age 1.

For cases where the sex was known, 57% occurred in boys, though the authors noted no substantial difference in number of cases between males and females in pediatric data from China, adding "the predominance of males in all pediatric age groups, including patients aged <1 year, suggests that biologic factors might play a role in any differences in COVID-19 susceptibility by sex."

Of 291 cases with known signs and symptoms, fever, cough, or shortness of breath was documented among 73% of pediatric patients versus 93% of adult patients ages 18-64. Notably, 56% of pediatric patients reported fever, 54% reported cough, and 13% reported shortness of breath. In fact, 53 of 78 patients without these symptoms had no symptoms reported, "but could not be classified as asymptomatic because of incomplete symptom information."

Data on hospitalizations was available for 745 pediatric cases, with the authors estimating a range of 5.7% to 20% of cases were hospitalized, with an estimated range of 0.58% to 2% admitted to an ICU. These figures were lower than adults ages 18-64, who had an estimated 10%-33% of patients hospitalized.

Infants accounted for the largest proportion of hospitalized children, ranging from 15% to 62% of pediatric COVID-19 admissions. Of 95 children younger than age 1, 59 were hospitalized and 5 were admitted to an ICU. Children ages 1-17 had a lower estimated range of hospitalization, from 4.1%-14%.

Among 345 pediatric cases with available information, 23% had at least one underlying condition. The most common were asthma in 40 children, cardiovascular disease in 25, and immunosuppression in 10. Among 295 cases with available information on hospitalization and underlying medical conditions, 28 of 37 hospitalized patients, including all 6 patients in the ICU, had one or more underlying medical conditions. Of 258 patients who were not hospitalized, 30 had underlying health conditions.

While three deaths were reported, the authors noted investigations are ongoing to determine if COVID-19 was the cause of death.

They added, clinicians should "maintain a high degree of suspicion" for infection in children and monitor the progression of illness, especially among those with underlying conditions.

"Because persons with asymptomatic and mild disease, including children, are likely playing a role in transmission and spread of COVID-19 in the community, social distancing and everyday preventive behaviors are recommended for persons of all ages to slow the spread of the virus," McNamara and colleagues wrote.

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