Research letter
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
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Respiratory syncytial virus (RSV) causes a high burden of disease in the months of autumn and winter, especially in infants. An average of 13 500 infants were treated for RSV infections as inpatients in Germany in 2010–2019, with a median inpatient stay of 5 days. 2.1% of these were receiving intensive inpatient treatment and 0.2% died (1). RSV infections occur cyclically; the RSV season usually lasts from October till March. Since 2024 the Standing Committee on Vaccination (STIKO) at the Robert Koch-Institute (RKI) has been recommending passive immunization against RSV for all infants before the start of their first RSV season or directly after birth if this falls into the RSV season (2). Nirsevimab is the first monoclonal antibody to become available for protection against RSV that is licensed for all infants regardless of pre-existing condition. In studies, nirsevimab has shown a high protective effect (88.4%) against hospitalization with RSV (3). We investigated whether changes in the epidemiology of RSV can already be observed at the end of the first RSV season in Germany since RSV prophylaxis was introduced.
Methods
In Germany, RSV infections have been notifiable nationwide according to §7 of the German Infection Protection Act since 2023; in Saxony they have been notifiable since 2002 on the basis of the Saxon Infection Protection Ordinance. We analyzed all nationwide RSV notification data made available to the RKI from seasons 2023/24–2024/25 as well as notification data from Saxony since the 2015/2016 season, stratified by age groups and hospitalization. We included all laboratory confirmed cases (nucleic acid/antigen confirmation or isolation of the pathogen), independently of clinical symptoms. A season is defined as the time period from calendar week (CW) 40 of a given year to CW 20 of the following year.
Results
In the 2024/2025 season, the RKI received notifications of 66 971 laboratory confirmed cases of RSV—slightly more than in the 2023/2024 season (57 137 cases; data status as of 10 June 2025). In infants (<1 year) the incidence fell by 54% (from 2291 cases/100 000 infants; 95% confidence interval [2255; 2326] in season 2023/2024 to 1045 cases/100 000 infants [1021; 1069] in season 2024/2025) (Figure). Only small changes to the preceding season were seen in toddlers and primary school children. As an example, in 1-year-olds, the incidence fell from 1146/100 000 [1121; 1170] to 1052/100 000 [1029; 1075]. By contrast, age specific rises in the incidence of up to 120% were seen in adults (with low initial numbers). In Saxony, similar age-specific changes to the previous seasons were seen (Table).
Nationwide, information on hospital admissions was available for 67% of RSV cases in infants. RSV associated hospitalizations in infants fell by 55%, from 6482 in the 2023/2024 season to 2899 in the 2024/2025 season; all hospital admissions were considered, regardless of whether the RSV infection was the reason for the hospital admission. Of the infants admitted to hospital in the 2024/2025 season, 55 received intensive inpatient care and one died (2023/2024: 121 intensive inpatient care, no deaths).
In the 2024/2025 season, immunization and hospitalization status were available for 38% of RSV cases in infants (2648 of 7208 cases): 85% of admitted and non-admitted infants were therefore not immunized.
Discussion
Our analysis of nationwide age-specific incidence rates of RSV indicate a substantial effect of the RSV monoclonal antibody prophylaxis for infants that was introduced in 2024. The RSV incidence may vary from season to season—as shown for Saxony in the Table, for example—but such a pronounced selective decline only in infants as a result of seasonal fluctuations seems unlikely.
Nationwide, RSV has been notifiable only since 2023, and in all experience it takes several years before robust conclusions about temporal trends are possible, the data should therefore be interpreted with caution. Data from Saxony, however, where state-specific notification has been mandatory since 2002, confirm the result. Comparisons with several prior seasons show a clear drop in incidence in the 2024/2025 season, isolated in infants.
Incidence rates in adults, which rose in the 2024/2025 season compared with the previous season, may actually be an indication of declining under-reporting rather than an increased burden of disease, owing to increased attention to RSV in adults and therefore more frequent testing. In infants, in whom RSV accounts for most seasonal respiratory infections and who are tested regularly for RSV in the inpatient setting, a more consistent implementation of the mandatory notification is more likely. On the background of the highly protective effect of nirsevimab published to date, the trend visible in our study seems to be accurate. Regional studies in other European countries have shown an even more pronounced decline in RSV-associated hospital admissions in this age group (69–77%), which depend on the achieved RSV immunization rates (4, 5).
Conclusions
Our analysis of notification data, in combination with experience gained in other countries and with highly effective RSV prophylaxis, provides initial indications of a clear reduction in the RSV burden of disease in infants since RSV prophylaxis was introduced in Germany. In spite of initial challenges in its introduction because of unclear reimbursement of costs as well as availability, the data presented here indicate an already broad implementation of the STIKO recommendation, although nationwide immunization rates are not yet available. The RKI is currently preparing detailed analyses regarding nationwide representative immunization rates, acceptance, and effect of RSV immunization. If an even greater proportion of infants in Germany can be immunized in future, the potential exists for substantially lowering the burden of RSV disease in this age group even further.
Funding
Federal Ministry of Health (project RAVE; reference number 2524PAT005).
Viktoria Schönfeld, Cornelius Rau, Wei Cai, Ole Wichmann, Thomas Harder
Conflict of interest statement
The authors declare that no conflict of interests exists.
Manuscript received on 6 May 2025, revised version accepted on 18 June 2025.
Translated from the original German by Birte Twisselmann, PhD.
Cite this as:
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. DOI: 10.3238/arztebl.m2025.0111
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