Younger adults with influenza and chronic conditions such as obesity, coronary artery disease (CAD), or chronic lung disease may have more severe influenza outcomes, including death, especially when unvaccinated. These are among study findings published in Open Forum Infectious Diseases.
In-depth studies related to influenza hospitalizations and deaths have focused largely on older adults and very young children. Therefore, investigators sought to determine clinical characteristics associated with severe outcomes among nonpregnant adults 18 to 49 years of age hospitalized with influenza in the US.
The investigators used data from the Influenza Hospitalization Surveillance Network (FluSurv-NET) to conduct a cross-sectional analysis that included non-pregnant adults in the US aged 18 to 49 years (n=16,140) who were hospitalized with laboratory confirmed influenza during the 2011-2012 through 2018-2019 seasons.
FluSurv-NET, which is sponsored by the Center for Disease Control and Prevention (CDC), is a US population-based surveillance system collecting data from each influenza season (October through April) on influenza-associated hospitalizations. Selected counties in 15 states (catchment population about 29 million) underwent surveillance across the 8 influenza seasons that were included in the current analysis. All patients included in the analysis had a positive influenza test during hospitalization or up to 14 days prior to hospitalization.
“
Chronic medical conditions such as coronary artery disease, chronic lung disease, and obesity are associated with more severe outcomes in adults aged 18-49 years hospitalized with influenza.
Among all included patients (median [interquartile range {IQR}] age, 39 [30-45] years; 52.0% women; 44.1% non-Hispanic White, 30.5% non-Hispanic Black, 12.3% Hispanic; 9.0% uninsured), 26.1% received a current season influenza vaccine prior to hospitalization (58.6% unvaccinated; 15.3% unknown vaccination status). Vaccination by race/ethnicity was as follow: 28.5% non-Hispanic White; 24.6% non-Hispanic Black; 22.9% Hispanic. The study excluded patients with hospital-onset influenza (ie, positive test >3 days after hospital admission). A third of patients (33.3%) currently smoked. The median time from symptom onset to hospital admission was 3 days (IQR, 1-4).
The most common chronic comorbidities included obesity (44.70%), asthma (32.04%), and diabetes (20.30%), and 84.3% of patients had at least 1 underlying condition. Across age groups, obesity was found in 50.7% of those 40-49 years; 45.8% of those 30-39 years; and in 30.9% of those 18-29 years. Across ethnic groups, obesity was found in 43.3% of non-Hispanic White patients; 48.4% non-Hispanic Black patients; 46.3% Hispanic patients.
Age groups 30-39 years and 40-49 years were significantly associated with an increased risk for severe outcomes (invasive mechanical ventilation [IMV] adjusted odds ratio [aOR], 1.25 and aOR, 1.36, respectively; death aOR, 1.28 and aOR, 1.69; respectively). These age groups were also more likely to develop pneumonia (aOR, 1.44 and aOR, 1.51), respectively.
Additional conditions associated with significantly increased risk included (1) being unvaccinated (intensive care unit [ICU] admission aOR, 1.18; IMV aOR, 1.25; death aOR, 1.48); and (2) having chronic conditions, including metabolic, cardiovascular, chronic lung, neurologic, or liver diseases, and extreme obesity (ICU aOR range, 1.22-1.56; IMV aOR range, 1.17-1.54; death aOR range, 1.43-2.36).
Among study limitations, FluSurv-NET data may not be nationally representative in that they cover about 9% of the US population, and the study may have unaccounted-for biases related to hospital admission practices.
“Chronic medical conditions such as coronary artery disease, chronic lung disease, and obesity are associated with more severe outcomes in adults aged 18-49 years hospitalized with influenza,” the investigators concluded. The study authors wrote, “To reduce the morbidity and mortality associated with influenza among adults aged 18-49 years, health care providers should strongly encourage receipt of annual influenza vaccine, and lifestyle/behavioral modifications particularly among those with chronic medical conditions.”
Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
