Weekly flu cases, hospitalizations and deaths have nearly doubled for the second week in a row, according to data from the Centers for Disease Control and Prevention.
So far this season, there have been at least 2.8 million illnesses, 23,000 hospitalizations and 1,300 deaths from influenza.
By comparison, the prior week's estimates had illnesses at 1.6 million, hospitalizations at 13,000 and deaths at 730.
Additionally, the cumulative hospitalization rate currently sits at 5 per 100,000, which is the highest at this point in the season since the 2010-11 season, as far back as statistics are available.
What's more, 6,465 new patients were admitted to hospital this past week with flu complications, according to the CDC, compared to 4,326 the previous week.
Fourteen states -- mostly in the southeast and south-central regions of the U.S. -- as well as New York City and Washington, D.C., are reporting "very high" levels of influenza-like activity.
Experts have stressed that getting the flu shot is the best way to protect Americans from severe illness and death, but vaccine uptake has been sluggish in comparison with previous flu seasons during the COVID-19 pandemic.
According to CDC data, flu vaccination among children remains similar to last season but is lower than two years ago.
As of the week ending Oct. 22, the latest date for which data is available, 24.8% have been vaccinated against flu in comparison with 32.1% at this time in October 2020.
CDC data shows that flu vaccinations among pregnant women are much lower compared to previous seasons.
At the end of September, the latest date for which data is available, 21% of pregnant women were vaccinated against the flu. By comparison, 26.4% had been vaccinated by the end of September 2021 and 38% had been at the end of September 2020.
This is especially concerning because pregnant women are more likely to fall severely ill and die compared to women who are not pregnant.
Receiving a flu shot can lower a pregnant woman's risk of being hospitalized from flu by around 40%, according to the CDC.
Additionally, a recent study jointly conducted by the CDC and the University of Auckland, in New Zealand, found that women who receive a flu vaccine have a lower risk of complications, including premature birth, low birthweight and stillbirth.
The newest data comes as the U.S. experiences a surge of respiratory illnesses, including respiratory syncytial virus, or RSV.
Data from the U.S. Department of Health and Human Services showed 78% of the estimated 40,000 pediatric hospital beds in the country are filled with patients -- the highest figure recorded in two years.
ABC News' Sony Salzman and Eric Strauss contributed to this report.