WASHINGTON (WTVO) — More children in the U.S. may have caught COVID-19 than previously thought.

The Centers for Disease Control and Prevention now estimates that three in four kids have been infected. Researchers examined blood samples from more than 200,000 Americans, looking for antibodies created by infections.

They found that the greatest increase was in those 17-years-old and younger. Antibodies in that group rose from roughly 45% in December to about 75% in February.

The CDC said that this is due to a surge in the omicron variant during that time.