Validity Is Limited

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

The reference values of the incidence data for RSV infections (population in the Figure and Table; infants in the text [1]) are used inconsistently. The decline in the infant population in Germany (more than 102 000 fewer children in 2021–2023) would explain part of the reduction in the incidence of RSV per head of population (2).

From the way of presentation using a mix of immunization and hospitalization status it is impossible to assess the nirsevimab prophylactic effectiveness. Only 15% of RSV cases documented by the Robert Koch-Institute (RKI) were immunized. The longitudinal data analysis was solely based on data from Saxony, which limits the generalizability of the findings. The numbers for 2015 (n=1755) and 2019 (n=1864), when the birth rate was higher, fall into a similar range as those in 2024/25. This indicates cyclical fluctuations in the RSV epidemiology, as in other European regions (2). Fluctuations in Saxony before 2014 were not shown.

The insufficiently precise diagnostic validation of data regarding RSV infections (inclusion of RSV antigen rapid tests with low specificity/sensitivity) and the lack of consideration of competitive population effects of other infections further impair the scientific meaningfulness/validity (3).

The two large trials leading to nirsevimab approval (MELODY, HARMONIE) were already subject to substantial methodological limitations (4). A causal association of the reduction in the incidence of RSV with the use to nirsevimab (as presented in [1]) is therefore scientifically not justifiable.

DOI: 10.3238/arztebl.m2025.0183

Prof. Dr. med. Tim Niehues

Helios Klinikum Krefeld, Lehrkrankenhaus der RWTH Aachen, Zentrum für Kinder- und Jugendmedizin, Krefeld

Conflict of interest statement

The author received travel expenses from the EMA and the Penta Research Foundation.

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 Germany for the seasons 2023/24 and 2024/25. Dtsch Arztebl Int 2025; 122: 472–3

2. Statistisches Bundesamt. Geburtenziffer 2023 auf 1,35 Kinder je Frau gesunken. Pressemitteilung Nr. 274 vom 17. Juli 2024.

3. Li K, Hamrin J, Nilsson A, et al.: Unraveling the role of viral interference in disrupting biennial RSV epidemics in northern Stockholm. Nat Commun 2025; 16: 8137

4. Arzneimittelkommission der deutschen Ärzteschaft. Stellungnahme zur frühen Nutzenbewertung gemäß § 35a SGB V: Nirsevimab (Erstmalige Dossierpflicht: Prävention von RSV-Infektionen, Kinder während ihrer 1. RSV-Saison, die nicht im Therapiehinweis zu RSV-Antikörpern adressiert sind). Berlin, 23. Juni 2025. Auftrag: A25–33, Version 1.0, Stand: 27.05.2025. https://www.akdae.de/stellungnahmen/amnog-fruehe-nutzenbewertung-nach-35a-sgb-v/wirkstoffe-a-z/newsdetail/nirsevimab (last accessed 22 October 2025)