People with Chronic Medical Conditions Continue to Account for The Majority of Flu Hospitalizations This Season

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January 26, 2024 – Today CDC posted new data that show the proportion of people hospitalized with flu this season in one CDC surveillance system who also have at least one chronic medical condition. Overall, among people hospitalized with flu, about 90% had a least one chronic medical condition. This is consistent with historical data. Annual flu vaccination and prompt flu antiviral treatment are especially important for people who are at higher risk of severe outcomes because they have chronic medical conditions.

Adults

According to preliminary data from the Influenza Hospitalization Surveillance Network (FluSurv-NET) from October through November 2023, 95% of adults hospitalized with flu had a least one reported chronic medical condition. This included:

  • 62% had hypertension (e.g., high blood pressure)
  • 45% had cardiovascular disease (e.g., history of heart attack, coronary artery disease)
  • 40% had metabolic disease (e.g., diabetes, thyroid disfunction)
  • 39% were considered obese
  • 33% had chronic lung disease (e.g., chronic bronchitis, cystic fibrosis)
  • 20% had asthma
  • 19% had neurologic disease (e.g., cerebral palsy, multiple sclerosis)

Only about 6% of adults hospitalized with flu had no known chronic medical condition. The FluSurv-NET data represents about 9% of the U.S. population.

Adults With Chronic Medical Conditions Historically Under-Vaccinated

While people who have certain chronic medical conditions are at higher risk of serious flu outcomes, they are historically under-vaccinated. During 2022-2023, only 49% of adults 18-64 years with selected chronic medical conditions got a flu vaccine. Those chronic medical conditions include asthma, diabetes, heart disease, chronic obstructive pulmonary disease (COPD), or cancers other than skin cancer. That proportion was similar the prior season. This season’s flu vaccination data for people with selected chronic medical conditions will be available in September. Flu vaccination coverage for all adults so far this flu season is about 47%, which is similar to coverage among adults at the same time last season (2022-2023).

Pregnant people also are more likely to experience severe flu illness that results in hospitalization compared to people of reproductive age who are not pregnant. This is because of changes to the immune system, heart, and lungs during pregnancy. According to FluSurv-NET, so far this season, 22% of reported flu-related hospitalizations in women 15-49 years have been in women who are pregnant. During the 2022-2023 flu season, 47% of people received a flu shot before or during pregnancy. So far, for the 2023-2024 flu season, overall coverage among pregnant people at the end of December 2023 (36%) is much lower than previous seasons.

Children

According to preliminary FluSurv-NET data from October through November 2023, 70% of children hospitalized with flu had at least one reported chronic medical condition. This included:

  • 27% had asthma
  • 20% were considered obese
  • 18% had neurologic disease
  • 6% had cardiovascular disease
  • 6% had chronic lung disease

Compared to adults, more children hospitalized with flu did not have a chronic medical condition (31%). However, children younger than 5 years—especially children younger than 2 years—are at higher risk of severe flu-related complications, including hospitalization, based on their age alone. Of the reported flu hospitalizations in children in FluSurv-NET, 78% were at higher risk of serious flu complication based either on a chronic medical condition or their age.

This week, CDC also reported 10 new flu-related deaths in children. So far during the 2023-2024 flu season, 57 flu-related pediatric deaths have been reported to CDC. The percentage of children that were not fully vaccinated this season is similar to what has been reported during previous seasons (about 80%).

Overall flu vaccination coverage among children this season as of January 13, 2024, is about 48%. This is about 3 percentage points lower compared with the same time last season (51%) and about 9 percentage points lower than it was in January 2020, before the COVID-19 pandemic (48% compared with 57%).

For 2023-2024, CDC estimates that between October 1, 2023, and January 20, 2024, there have been at least 210,000 hospitalizations among children and adults due to flu. Based on the number of flu-related hospitalizations reported by FluSurv-NET sites, the overall cumulative hospitalization rate between October 1, 2023, and January 20, 2024, is 43.3 per 100,000 population.

In addition to annual vaccination to reduce the risk of getting flu or developing serious flu complications, CDC recommends prompt treatment with a flu antiviral medication for people who have flu or suspected flu who are severely ill (are hospitalized) or who are at higher risk of serious flu-related complications. Treatment with flu antivirals is recommended as soon as possible for people who are hospitalized with flu or people who are at higher risk for severe disease. Flu antiviral medications can lessen symptoms and shorten the duration of illness by 1 or 2 days, and they might also prevent some flu complications, like pneumonia. Antiviral treatment is especially important for people at higher risk of serious flu complications and can mean the difference between milder or more serious illness possibly resulting in a hospital stay. Data show that antiviral medications are under-utilized among some groups of people, including children. It’s important that providers follow CDC recommendations for flu prevention and treatment.