"We're looking at the definition right now and more to come there," Walensky said during a press briefing on Wednesday.
The CDC's current guideline recommends citizens to receive a booster shot amid the winter surge of the novel coronavirus.
The Omicron is now the dominant coronavirus variant in the United States, accounting for more than 73% of new cases as of last week, according to the CDC.
Walensky said the latest US seven-day average of cases has increased by a quarter to nearly 150,000 amid the growing prevalence of the Omicron variant.