A much higher percentage of children in Northern Virginia appear to have been exposed to the COVID-19 virus than previously believed, according to a new study released March 18.

An antibody study conducted from July to October by Inova Health System, the Virginia Department of Health and George Mason University found that the overall antibody positivity rate in children ages 0 to 19 was 8.5%.

In addition, two-thirds of the children who had antibodies had no history of symptoms of COVID-19 infection. That highlights the silent, or asymptomatic, infection in children and subsequent risk of transmission of infection to others, Inova said in a news release.

Through the end of October, Northern Virginia as a whole had reported about 58,000 confirmed and probable cases of coronavirus, representing only 2.5% of the region’s population. Following the post-holiday surge, cases have nearly tripled, to a total of about 164,000, or about 7.1% of the region’s population.

The Inova study analyzed blood samples from more than 1,000 children, with those of Hispanic origin found to have the highest rate of antibody positivity, 26.6%.

COVID-19 antibodies were found in 8.2% of white children, 5.3% of Black children, 5.7% of Asian children, and 16.2% of children with multiple racial origins.

Broken down by age groups, the rate was 13.7% in young children (0-5 years), 7.5% in elementary school-age (6-10 years), 5.1% in early adolescents (11-15 years) and 10.8% in older adolescents (16-19 years).

Compared with an earlier study of adults in Virginia, which reported a COVID-19 antibody positivity rate of 4.4%, the pediatric rate of positivity is nearly double.

“The pediatric serology project unexpectedly found more children were seropositive than we had anticipated,” said Dr. Rebecca Levorson, division director for pediatric infectious diseases at Inova Children’s Hospital.

“Most of these children did not have symptoms, which makes it difficult to know who may be infectious and who is not at a specific time,” she added. “Nearly a quarter of the U.S. population is children, and as they may represent a larger proportion of SARS-CoV-2 disease than we previously thought, we need to recognize that children will continue to be infected with and possibly asymptomatically spread this disease.”

More information about the pediatric serology project can be found at bit.ly/NoVa_Antibodies.