WASHINGTON — A top U.S. public health official says young people are driving the latest uptick in COVID-19 cases, as the increasing rate of vaccination in older Americans is preventing the most serious cases among seniors.

Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, said during a briefing Monday that “cases are increasing nationally, and we are seeing this occur predominately in younger adults.”

She cites the increasing spread of variants, but also a rise in youth sports and extracurricular activities as contributing to the steady increase in cases over the last four weeks.

But Walensky pointed to positive developments among the most vulnerable age group, saying senior citizens' virus deaths have reached their lowest levels since the early fall. Greater than 75% of those aged 65 or older nationally have received at least one dose of a COVID-19 vaccine and nearly 55% are fully vaccinated.

“What we’re seeing is both a decrease in emergency department visits as well as hospitalizations associated with that demographic," Walensky said.