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Among adults with outpatient respiratory syncytial virus (RSV) infections across six RSV seasons, roughly one in 20 were hospitalized within 28 days, according to a large cohort study that used data from three health record databases.

In the cohort of over 67,000 patients with outpatient medically attended RSV infections, hospitalization rates were 4.5% to 6.2%, and 6.5% to 8.5% in a high-risk subgroup, across the three databases, reported Joshua T. Swan, PharmD, MPH, of Pfizer in New York City, and colleagues in .

High-risk features included age 65 and older, asthma, chronic obstructive pulmonary disease (COPD), and congestive heart failure (CHF). Across the patients in the three databases, comorbidity prevalence were 20% to 30.5% for COPD, 14.6% to 24.4% for CHF, 14.6% to 24.4% for asthma, and 14% to 54.5% for age 65 and over.

Infection rates for RSV have been underestimated, partly due to underutilization of testing for the viruses, Swan and team noted. Although there are three available vaccines against RSV, there are few approved treatments for it.

"Therapeutic and preventive measures to reduce hospitalizations following RSV infection would provide major benefits to patients in the U.S. healthcare system," they wrote.

Swan told 番茄社区 that "the absolute risk of hospitalization of one out of 20 patients observed in our study represents significant and meaningful risk for vulnerable adults."

Much of the public's attention has historically focused on the risk of hospitalization for young children with RSV, he added.

Prior studies have suggested that 82% to 90% of hospitalizations observed within 28 to 30 days of RSV diagnosis in adults were related to acute respiratory infection, the authors noted.

Cameron Wolfe, MBBS, of Duke University Medical Center in Durham, North Carolina, told 番茄社区 that the study's results "confirm what we've been worried about for a while, which is that similar to flu, and more recently COVID, we see a lot of older adults, and those at risk ultimately require hospitalization after RSV."

"An additional strength is that this [study] isn't trying to tease out only those admitted with RSV pneumonia," he added. "We've known for a while that some heart attacks are triggered by the stress of a bad viral infection, so are some strokes, so are some bouts of dehydration and falls, etc."

There are no antiviral drugs that have been proven effective against RSV, Wolfe noted. "Testing is relevant for RSV only in that it helps you put a name to the illness at hand and proves you don't need antivirals for, say, COVID or flu, or antibiotics for bacteria."

For this study, Swan and colleagues analyzed closed claims data on RSV outpatient encounters from the electronic health records in three de-identified databases -- Optum's Integrated Claims-Clinical dataset, TriNetX Linked, and Veradigm Network EHR -- from October 2016 through September 2022, covering six RSV seasons. Open claims were not included, and all patients had commercial or government insurance.

The researchers identified 67,239 RSV infections diagnosed in adult outpatients: 2,771 from Optum, 7,442 from TriNetX, and 57,026 from Veradigm. Most infections occurred among women (62-67%).

The sites of the outpatient diagnoses included clinics and emergency departments.

The percentage of patients who were hospitalized varied by database. The proportion of RSV patients who were hospitalized was 6.2% in Optum, 6% in TriNetX, and 4.5% in Veradigm. In the high-risk subgroup, these rates were 7.6%, 8.5%, and 6.5%, respectively.

Swan and team noted that the RSV infections identified in the databases via a positive laboratory test result or a diagnosis code underrepresented the true number of RSV events during the time period. "For this reason, study findings can only be applied to RSV infections that are identified in an outpatient setting and cannot be used to estimate the true burden of RSV infections in the larger population," they wrote.

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