Estimated Incidence of Respiratory Syncytial Virus (RSV)-related Hospitalizations for Acute Respiratory Infections (ARIs), including Community Acquired Pneumonia (CAP), in Adults in Germany
Authors: Liang Caihua , Begier Elizabeth , Hagel Stefan , Ankert Juliane , Wang Liz , Schwarz Claudia , Bayer Lea J. , von Eiff Christof , Liu Qing , Southern Jo , Vietri Jeffrey , Uppal Sonal , Gessner Bradford D. , Theilacker Christian , Pletz Mathias 
Published: June 2024

AbstractBackgroundRSV is a leading cause of ARI, including CAP, in older adults, but available data often substantially underestimate incidence. We estimated RSV-related ARI hospitalization incidence from a prospective CAP study and adjusted for undiagnosed RSV infections due to use of nasopharyngeal/nasal swab testing only.MethodsWe conducted active, population-based surveillance of adult CAP hospitalizations in Thuringia (Germany) between 2021–2023. Participant nasopharyngeal/nasal swabs were RSV-tested by multiplex nucleic acid amplification testing. To estimate RSV-related CAP incidence, age-group specific proportions of RSV positivity among tested patients were applied to all-cause CAP incidence. To adjust for underdiagnosis due to nasopharyngeal/nasal swab sampling only and the percentage of ARI with pneumonia diagnoses, we used data from a large, prospective, multispecimen study assessing impact of collecting multiple specimens (nasopharyngeal/nasal swab, saliva, paired serology, and sputum) among 3,669 adults hospitalized for ARI.ResultsAmong 1,040 enrolled adults (≥18 years) with radiologically confirmed CAP, 38 tested RSV-positive via nasopharyngeal/nasal swab (3.7%). The percentage positive increased to 7.8% after adjusting for higher RSV detection with multiple specimens compared to nasopharyngeal/nasal swab only. Adjusted RSV-related CAP hospitalization rates were 4.7 (95%CI 1.5–11.2) and 109.1 (95%CI 89.6–131.6) per 100,000 adults aged 18–59 and ≥60 years, respectively. Adjusted incidences of RSV-related ARI were 18.4 (95%CI 11.0–28.9) and 377.6 (95%CI 340.5–417.7) per 100,000 adults aged 18–59 and ≥60 years, respectively. Among RSV-positive CAP hospitalizations, 12.1% of patients aged ≥65 years died within 30 days, with no deaths in those aged 18–64 years. Cardiovascular events occurred in 11.1% of patients aged 18–64 and 36.4% of those aged ≥65 years.ConclusionsOlder adults in Germany face a high burden of RSV-related ARI hospitalizations, including CAP, underscoring RSV vaccination’s potential utility for this population.KEY PUBLIC HEALTH MESSAGEWhat did you want to address in this study and why?Hospital administrative data significantly underestimate respiratory syncytial virus (RSV) incidence due to infrequent testing and lower sensitivity of single nasopharyngeal/nasal swab testing among adults. No prospective incidence studies are available for Germany and most other European countries. We aimed to estimate RSV-related acute respiratory infection (ARI) hospitalization incidence from a prospective community-acquired pneumonia (CAP) study and adjust for undiagnosed RSV infections due to limited testing and use of nasopharyngeal/nasal swab testing only. Detailed data on RSV disease burden are crucial for developing vaccination policies.What have we learnt from this study?Adjusted annual incidence of RSV-related ARI rates were 18.4 (95% CI 11.0–28.9) and 377.6 (95% CI 340.5–417.7) per 100,000 population for adults 18–59 and ≥60 years, respectively. Among RSV-positive CAP hospitalizations, 12.1% of patients aged ≥65 years died within 30 days, with no deaths in those aged 18–64 years. Cardiovascular events occurred in 11.1% of patients aged 18–64 and 36.4% of those aged ≥65 years.What are the implications of your findings for public health?Our findings are similar to recent time-series incidence results from Germany (236–363/100,000 for adults ≥60 years) and underscore the substantial burden of RSV among adults, particularly the high rate of cardiovascular events contributes to a probably underestimated burden of RSV disease.