Worst flu outbreak in more than a decade spikes hospitalizations

The big picture: Flu-connected hospital admissions over Thanksgiving week almost doubled over the previous week and were the highest seen for that period since the 2010-2011 season, per the CDC.

• Adults 65 and older and kids 4 and under have been hit particularly hard during the unusually early surge, especially if they had underlying health conditions.
• But about 4 in 10 Americans say they don't plan to get a flu shot this season, largely over concerns the vaccines don't work well or have side effects.
• The Biden administration is promising resources and personnel to help local health systems cope but isn’t considering declaring a public health emergency, CNN reported.

Go deeper: Public health experts say that masking and other pandemic precautions largely kept influenza at bay over the past two years and disrupted its seasonal spread. But the return to pre-pandemic life has left us "immunologically naïve" and more susceptible to infections.

• Normally, "we might get exposed to a small bit of virus and your body fights it off," John Tregoning, an immunologist at Imperial College London, told Nature. But, he added, "that kind of asymptomatic boosting maybe hasn't happened in the last few years."
• One research team last year predicted strong epidemic rebounds in children once personal protection measures were lifted and urged robust "catch-up vaccination programs."
• But experts caution they still don't know a lot about seasonal viruses and continue to grapple with questions like how much COVID-19 weakened the public's immunity.

The flu outbreak comes as other respiratory diseases are circulating, including respiratory syncytial virus, or RSV, and emerging COVID variants.

• The CDC estimates that so far this season, there have been at least 8.7 million illnesses, 78,000 hospitalizations and 4,500 deaths from the flu.

What they're saying: "We can't let up our guard. We have to take the precautions that we need to prevent the spread of these viruses, like washing our hands, wearing masks in crowded indoor spaces, and like making sure that we're staying home if we're sick. And of course, again, with COVID and flu [to] get vaccinated as soon as you can," U.S. Surgeon General Vivek Murthy told ABC's "Good Morning America."

What we're watching: There's particular concern about pregnant women and some racial and ethnic groups. Flu vaccine uptake at this point for pregnant women is 12.1 percentage points lower than in 2021 and 21.7 percentage points lower than in 2020, the Center for Infectious Disease Research and Policy at the University of Minnesota noted.

• Flu hospitalization rates were nearly 80% higher in Black adults than in white adults from 2009 to 2022, per the CDC. And less than 43% of Black, Hispanic and Native American adults were vaccinated during the 2021-2022 flu season.
• The federal government could step in to help stressed health providers, like by allowing hospitals with staffing shortages use waivers to surge capacity or make it easier to transfer patients with flu, COVID or RSV, Health and Human Services Secretary Xavier Becerra wrote to states in a letter CNN obtained.
• The CDC also has $400 million in funding to respond to health threats like the flu, along with data analysis and other resources, per the letter.

The bottom line: The COVID-19 threat may be more manageable, thanks to vaccines, antivirals and tests. But the pandemic experience may have left us more vulnerable to waves of other seasonal illnesses that are complicating the return to normal.