In a comprehensive review published in The Journal of Infectious Diseases, researchers conducted a global, comprehensive literature review of observational studies reporting incidence of RSV in adults and sought to ascertain current evidence gaps.

For this study, the researchers searched PubMed and Embase for English-language publications from 2000 to 2022 and congress abstracts from 2019 to 2021 that reported RSV incidence rates or cumulative incidence. The review included observational studies that reported RSV incidence in adults. Cross-sectional studies, case series, and other designs estimating only RSV frequency were excluded. Data were extracted by age group and underlying condition where available, and the search included all geographic areas.

The researchers analyzed the studies for variability in RSV incidence across different populations and geographies, identified critical gaps in the current knowledge, and suggested additional research with consistent case definitions and surveillance strategies.

Out of 528 potentially relevant records, 37 primary studies were deemed appropriate for this review. The majority of the evidence came from high-income regions. About two-thirds of the studies reported RSV incidence in hospital settings. Fifteen studies specifically included or focused on adults with underlying conditions. There was considerable variation in how incidence was measured and presented across studies. RSV incidence estimates varied extensively both within and between different geographic regions. Generally, RSV incidence increased with age and was most significant among adults with underlying health conditions.

Four studies from the United States reported RSV incidence among populations with cardiopulmonary conditions, with the estimate as high as 18,000 per 100,000 person-years reported in patients with chronic obstructive pulmonary disease or congestive heart failure in a prospective cohort study.

The authors wrote, “Another surveillance study in the United States estimated the ranges of annual incidence (per 100,000 population hospitalized) for RSV-associated ARI [acute respiratory infection] (PCR [polymerase chain reaction]-confirmed) among adults with comorbidities.

“This review identified observational studies reporting RSV incidence in adults (≥18 years) in diverse populations globally. As studies varied in the case definitions used, the type of incidence reported, the time frame of reported incidence, and the age groups used, comparing results across studies is challenging. Overall, RSV incidence increased with age in all populations, with the highest rates observed in older adults with underlying conditions.”

The authors also noted that with the introduction of adult RSV vaccines, it is essential to understand the baseline burden of RSV across various geographies and population characteristics to estimate their impact accurately for patient populations who should receive them.

The authors concluded, “Estimates of RSV incidence are highly variable across populations and geographies. Further population-based studies with well-defined, consistent case definitions and surveillance strategies are needed for accurate and comparable estimates of RSV incidence, particularly in the geographic regions identified by the gap analysis.”

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