In Reply

Letters to the editor regarding the article The Incidence of RSV Infection Since the Introduction of Monoclonal Antibody Prophylaxis An Analysis of Reported Case Data Across Germany for the Seasons 2023/24 and 2024/25 by Viktoria Schönfeld, Cornelius Rau, Wei Cai, Ole Wichmann, and Thomas Harder in issue 17/2025

We would like to thank Niehues for his comments on our research letter (1). We reported mainly incidence rates—both for the nationwide analyses and for Saxony (2). Incidence rates allow populations of different sizes to be compared, based on 100 000 inhabitants of the population group in question (e.g. infants). To illustrate the healthcare perspective, hospital admissions were also reported as absolute case numbers. We used population data from the German Federal Statistical Office (3) to calculate incidence rates (as of 31 December of the respective year; due to initially lacking data for 2024, the data of the preceding year were used). Data published in the meantime show that the number of children under one year of age decreased by 2.4% from 2023 to 2024 (annual fluctuation range since 2019: −8.41% to +2.84%), which does not explain an incidence reduction of 54%.

Additional factors may affect the RSV epidemiology and cannot be differentiated in ecologic studies such as ours. However, in the complete overview of international studies (4) it seems likely that the introduction of nirsevimab did not merely coincide with the isolated reduction in the RSV incidence in infants, but actually caused it.

DOI: 10.3238/arztebl.m2025.0184

On behalf of the authors

Dr. med. Viktoria Schoenfeld

Robert Koch Institute Berlin

Conflict of interest statement

The author declares that no conflict of interest exists.

References

1. Schönfeld V, Rau C, Cai W, Wichmann O, Harder T: The incidence of RSV infection since the introduction of monoclonal antibody prophylaxis: An analysis of reported case data across ermany for the seasons 2023/24 and 2024/25. Dtsch Arztebl Int 2025; 122: 472–3

2. Kuhn J, Bolte G: Epidemiologie und Sozialepidemiologie. In: Bundeszentrale für gesundheitliche Aufklärung (BZgA) (eds.): Leitbegriffe der Gesundheitsförderung und Prävention. Glossar zu Konzepten, Strategien und Methoden. 2024.

3. Statistisches Bundesamt (Destatis) (2025): Fortschreibung des Bevölkerungsstandes. Zuletzt aktualisiert am 25.09.2025. www-genesis.destatis.de/datenbank/online/statistic/12411/table/12411-0005 (last accessed on 13 October 2025).

4. Lee B, Trusinska D, Ferdous S, et al.: Real-world effectiveness and safety of nirsevimab, RSV maternal vaccine and RSV vaccines for older adults: A living systematic review and meta-analysis. Thorax 2025: thorax-2025–223376