Estimated Incidence of Respiratory Syncytial Virus (RSV)-related Hospitalizations for Acute Respiratory Infections (ARIs), including Community Acquired Pneumonia (CAP), in Adults in Germany

BackgroundRSV 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 vaccinations potential utility for this population. KEY PUBLIC HEALTH MESSAGEO_ST_ABSWhat did you want to address in this study and why?C_ST_ABSHospital 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.