Adults with respiratory syncytial virus (RSV) who are hospitalized are likely to experience worse outcomes than those hospitalized with influenza, based on data collected over the past 3 respiratory illness seasons. These are among the findings of a multicenter, prospective study published in Clinical Infectious Diseases.

Although RSV has long been considered a children’s disease that is most severe in those aged 2 years and younger, the virus also affects adults and can have severe consequences, especially in those who are immunocompromised, older and frail, and/or have comorbidities including congestive heart failure (CHF) and chronic obstructive pulmonary disease (COPD).

To address the lack of research for guiding RSV vaccination strategies among high-risk adults, researchers sought to describe the clinical severity and frequency of RSV infection among hospitalized adults over 3 respiratory illness seasons (between September 2016 to and May 2019). Toward that end, the investigators identified and compared the population characteristics and clinical outcomes of adult inpatients with influenza, RSV, and other acute respiratory infections.

The study was conducted in conjunction with the Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) site in Michigan, which gathered data on patients with acute respiratory illnesses from surveillance sites in 4 states: Michigan, Pennsylvania, Tennessee, and Texas. A total of 11,369 adults who were hospitalized with acute respiratory illness were enrolled in the HAIVEN study across the 3 respiratory seasons evaluated. Following exclusions, the total study population comprised 10,311 inpatients, including: 26.0% (2679 of 10,311) of participants from 2016 to 2017; 37.7% (3885 of 10,311) of participants from 2017 to 2018; and 36.3% (3747 of 10,311) of participants from 2018 to 2019.

Participating patients had respiratory specimens collected within 10 days or less of onset of illness and within 72 hours or less from hospitalization. Specimens collected from throat and nasal swabs were tested for RSV and influenza with the use of real-time reverse transcription polymerase chain reaction (RT-PCR).  Self-reported data were also collected regarding date of onset of illness; patient demographics; frailty score; and influenza vaccination status.

In this prospective, multi-site study, we have confirmed the importance of RSV as cause of a significant proportion of hospitalization in adults.

For the current RSV analysis, descriptive statistics were computed for the following variables: (1) age groups (18 to 49 years, 50 to 64 years, 65+ years); (2) sex/gender; (3) race/ethnicity (White non-Hispanic, Black non-Hispanic, other non-Hispanic, Hispanic); (4) body mass index (BMI); (5) Charlson Comorbidity Index (CCI) scores; (6) asthma; (7) CHF; (8) COPD; (9) frailty; (10) site (Michigan, Pennsylvania, Tennessee, or Texas); (11) respiratory season evaluated (2016 to 2017, 2017 to 2018, or 2018 to 2019); and (12) influenza vaccination status.

Investigators detected RSV in 6.0% (622 of 10,311) of patients vs influenza in 18.8% (1940 of 10,311) of patients. Among the remaining 75.2% (7749 of 10,311) of patients with acute respiratory illness, no cases of influenza or RSV were detected.

The proportion of adults with CHF was significantly higher among those with RSV than those with influenza (37.3% vs 28.8%, respectively; P <.0001). Additionally, the percentage of adults with COPD was significantly higher among those with RSV than those with influenza (47.6% vs 35.8%, respectively; P <.0001).

Patients with RSV more often experienced a longer hospital length of stay (LOS) than those with influenza (odds ratio [OR], 1.38; 95% CI, 1.06 to 1.80) when hospitalizations of longer than 1 week were considered. Participants with RSV also required mechanical ventilation more frequently than did those with influenza (OR, 1.45; 95% CI, 1.09 to 1.93).

Participants with RSV exhibited twice the odds of having a comorbidity index score of at least 3 compared with participants with influenza — a finding that was statistically significant (adjusted OR [aOR], 2.10; 95% CI, 1.50 to 2.93; P <.0001). Moreover, in comparing patients with RSV with patients who were either influenza-negative or RSV-negative, investigators found that detection of RSV was significantly associated with obesity (aOR, 1.29; 95% CI, 1.02 to 1.63; P =.03) and a patient age of 65 years or older (aOR, 1.65; 95% CI, 1.30 to 2.10; P <.0001).

Several potential study limitations warrant mention. First, the required study testing did not include RSV subtype. In addition, data regarding death post hospital discharge were missing for a number of observations, thus limiting outcome analysis. Another limitation involves the impact of missing enrollments, which occurred either because of refusal on the part of eligible participants or because of missing admissions due to hospital understaffing.

The study authors concluded that “In this prospective, multi-site study, we have confirmed the importance of RSV as cause of a significant proportion of hospitalization in adults. We found those with underlying cardiopulmonary conditions to be a critical target for future campaigns as vaccines become available, and our data highlight the need for RSV prevention and testing for adults, including adults younger than 65 years of age.”

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

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