Centers for Disease Control and Prevention influenza experts are concerned that the United States could be at risk for a severe flu season this year, Director Dr. Rochelle Walensky warned Wednesday.

That’s because the U.S. population may now have reduced immunity against influenza after seasonal flu cases reached an all-time low last year when large parts of the nation were shut down, Walensky told reporters during a White House press briefing.

During the 2020 flu season, there were very few flu cases, “largely because of masking and physical distancing and other prevention measures put in place for the Covid-19 pandemic,” she said.

Walensky urged Americans to get vaccinated for both Covid and the flu, saying vaccinations are not just important for ending the pandemic but also preventing other infectious diseases. An increase in flu infections this winter could put an additional burden on the nation’s health-care system, increasing stress on health care workers who are already fighting a high number of hospitalizations due to Covid, she said.

“We continue to see many hospitals and intensive care units across the country at full capacity,” she said. “Each year in the United States, influenza can claim between 12,000 and 52,000 lives and result in 140,000 to 710,000 hospitalizations.”

This is a developing story. Please check back for updates.