RSV in Hospitalized Adults 60 and Older: Rarer but More Severe Than COVID-19 or Flu

Respiratory syncytial virus (RSV) is increasingly recognized as a cause of severe respiratory illness in older adults: each year in the U.S. it causes an estimated 60,000–160,000 hospitalizations and 6,000–10,000 deaths among people 65 and older. On June 21, 2023, CDC's Advisory Committee on Immunization Practices recommended the first RSV vaccines for adults 60 and older, through shared clinical decision-making between patient and provider. That decision depends on knowing how severe RSV is — compared with COVID-19 and flu.

The study

The IVY Network enrolled adults 60 and older hospitalized with acute respiratory illness at 25 hospitals in 20 states, February 1, 2022–May 31, 2023. Everyone was tested centrally for RSV, SARS-CoV-2 and influenza; people with more than one of the three were excluded.

Median ages were similar (72 RSV, 74 COVID-19, 71 flu), and so was the burden of chronic illness. 81.5% had had at least one COVID-19 vaccine and 48.3% a seasonal flu shot. RSV and flu admissions were strongly seasonal; COVID-19 much less so.

Hospital admissions by virus over time. Image from CDC's report

RSV was more severe

After adjusting for age, sex, race and ethnicity, chronic conditions and region, patients with RSV were more likely to need more care:

Why RSV looked worse than COVID-19

Earlier comparisons, from 2020, found COVID-19 the more severe. The difference now likely reflects milder Omicron sublineages, much more immunity from vaccination and infection, and wider use of antiviral treatment for COVID-19. RSV is also less common among hospitalized patients, so clinicians may not think of it as a serious threat in older adults.

What it means for vaccination

The trials behind FDA approval of the RSV vaccines weren't designed to measure protection against hospitalization in people 60 and older, but both showed moderate to high efficacy against lower respiratory tract disease, which leads to severe illness. More study is needed, but vaccination is currently the only approved RSV prevention product for older adults. The severity of RSV should weigh in older adults' and providers' shared decisions about getting vaccinated.

Limits: sicker patients may have been more likely to be tested for RSV — though central testing of 5,955 other enrollees found only 25 (0.4%) with unrecognized RSV; results weren't stratified by vaccination or treatment; and the sample was too small to look at death alone.

Sources

Based on Diya Surie, Katharine A. Yuengling, Jennifer DeCuir and others, "Disease Severity of Respiratory Syncytial Virus Compared with COVID-19 and Influenza Among Hospitalized Adults Aged ≥60 Years — IVY Network, 20 U.S. States, February 2022–May 2023," MMWR, volume 72, Centers for Disease Control and Prevention; a work of the United States government in the public domain.