BACKGROUND:Real-world evidence on nirsevimab impact beyond the first season when given under universal immunisation programmes is emerging. We aimed to assess the medium-term impact of universal infant respiratory syncytial virus (RSV) prophylaxis with nirsevimab across inpatient and outpatient settings during two consecutive RSV seasons. METHODS:NIRSE-GAL is an ongoing, population-based, prospective, longitudinal study in Galicia, Spain. For this study, we included all infants eligible for nirsevimab in the 2023-24 RSV campaign in Galicia, followed up from their first RSV season (2023-24) until the end of their second RSV season (2024-25). The primary endpoint was RSV-related lower respiratory tract infection (LRTI) hospitalisation. Secondary endpoints were LRTI hospitalisation, acute bronchitis or bronchiolitis hospitalisation, pneumonia admissions, all-cause hospitalisations, and primary health-care outcomes (acute bronchitis or bronchiolitis, wheezing or asthma, LRTI, respiratory infections, acute otitis media, and all otitis diagnoses). The first recurrences of these endpoints were also assessed as secondary endpoints. Impact was estimated by Poisson regression models using weekly incidence rates of historical non-pandemic seasons (2017-18 to 2022-23) as comparators, adjusted for RSV seasonality, and evaluated across three follow-up periods: the first RSV season, the second RSV season, and up to 18 months. This study is registered with ClinicalTrials.gov, NCT06180993. FINDINGS:Of 12 492 eligible infants, 11 796 received nirsevimab (94·4% coverage). Compared with historical cohorts, RSV-related LRTI hospitalisations decreased by 85·9% (95% CI 80·2-90·0) in the first season and 55·3% (22·5-74·3) in the second, with an estimated 123 infants needing to be immunised to prevent a second-season admission. First LRTI hospitalisations decreased by 59·8% (46·5-69·8) in the first season and 48·1% (33·1-59·7) up to 18 months. Acute bronchitis or bronchiolitis admissions decreased by 59·0% (37·9-72·9) in the first season and 58·7% (40·6-71·3) up to 18 months. All-cause hospitalisation declined by 20·3% (3·1-34·4) in the first season, with no significant reduction thereafter. First recurrent admissions in the second season decreased by 78·2% (25·6-93·6) for RSV-related LRTI, 62·4% (30·9-79·6) for LRTI, and 76·9% (5·3-94·4) for acute bronchitis or bronchiolitis. First outpatient visits declined during the first season by 30·8% (17·5-41·9) for bronchitis or bronchiolitis, 33·4% (21·6-43·4) for LRTI, and 27·7% (14·9-38·5) for wheezing or asthma. First recurrent outpatient visits also declined, by 52·5% (39·7-62·6) for acute bronchitis or bronchiolitis, 28·2% (17·8-37·3) for wheezing or asthma, and 47·3% (35·3-57·2) for LRTI. INTERPRETATION:Universal infant nirsevimab prophylaxis markedly reduced RSV-related hospitalisations and outpatient morbidity, with sustained reductions in RSV-related LRTI hospitalisations into the second season and no signal of adverse shift in RSV morbidity. These findings provide robust population-level evidence that could be valuable for infant immunisation policies and cost-effectiveness models. FUNDING:Sanofi and AstraZeneca. TRANSLATION:For the Spanish translation of the abstract see Supplementary Materials section.

CONTEXT:Nirsevimab was implemented in Europe and the United States in September 2023. While its effectiveness in preventing respiratory syncytial virus (RSV)-bronchiolitis has been demonstrated by real-life studies, its impact on mid-term child health, quality of life, and parental absenteeism remains unstudied. METHODS:Infants under 1-year with a first bronchiolitis episode were recruited through the OURSYN study involving 37 primary care pediatricians in France between 2021 and 2025 (pre-nirsevimab period: 02/2021-03/2023 and nirsevimab period: 09/2023-03/2025). RSV status was determined by antigenic nasopharyngeal testing. At day 15, parents reported symptoms, quality of life (PedsQL Infant), and work absenteeism. Their associations with (i) RSV status, (ii) period of inclusion, and (iii) nirsevimab immunization status among RSV-positive cases were assessed using multivariable logistic regression adjusted for confounders. RESULTS:Among 1870 bronchiolitis cases included, 637 (34.0%) occurred during the nirsevimab period and 812 (43.4%) were RSV-related. Over the study period, at day 15, RSV-cases had more feeding difficulties (aOR = 1.41 [1.06-1.88]), longer daycare absence (4.7 vs. 3.2 days), and more parental absenteeism (aOR = 1.61 [0.99-2.62]) compared to RSV-negative. The proportion of RSV-cases decreased during the nirsevimab period compared with the pre-nirsevimab period (47.1% vs. 35.7% P < .001). Bronchiolitis cases recruited during this period had shorter daycare absences (3.2 vs. 4.3 days). Among RSV-cases, immunized infants had lower risk of persistent fever (aOR = 0.14 [0.01-0.79]). CONCLUSION:This large prospective study provides the first evidence that the mid-term burden of RSV-bronchiolitis in infants may be reduced following the implementation of nirsevimab, with potential benefits for infant health, quality of life and parental absenteeism.

BACKGROUND:Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections (LRTI) in infants and young children. While considerable research has described the clinical burden and direct medical costs of RSV in Germany, the broader economic impact remains poorly understood, particularly the burden on affected families and productivity losses associated with parental work absence. METHODS:The prospective, multicenter PAPI study was conducted across 12 hospitals and five pediatric practices in Germany during the 2021-2022 and 2022-2023 RSV seasons. Children under 24 months presenting with lower respiratory tract infections were tested for RSV. Health care resource use, parental expenses, and absenteeism were assessed through questionnaires and follow-up interviews. The human capital approach was used to estimate productivity losses. RESULTS:Of 1,607 hospitalized children, 918 (57.1%) tested positive for RSV and 714 were included in the analysis. In the outpatient setting, 286 of 1,442 cases (19.8%) were RSV-positive, with 250 included in the analysis. Among hospitalized RSV cases, 91.3% required additional primary care visits. Parental work loss was reported in 64.3% of hospitalized and 37.5% of outpatient cases. Mean productivity losses were €1,865 for hospitalized cases and €1,484 for outpatient cases associated with parental work loss. Productivity losses were higher for toddlers (aged 12-23 months) than infants (0-11 months), with hospitalized toddlers showing the highest mean loss of €2,584 per case involving parental work absence. CONCLUSIONS:This study demonstrates that RSV infections in children under two years impose a substantial economic burden on the German health care system and parents. The findings provide critical evidence to support decision-making on preventive strategies aimed at reducing RSV-related morbidity and its economic consequences in Germany.

OBJECTIVES:Respiratory syncytial virus (RSV) is a major cause of morbidity globally, with most cases managed in outpatient settings. However, data characterizing the disease burden of non-severe RSV infections remain limited. METHODS:The prospective, multicenter pediatric airway pathogen incidence (PAPI) study enrolled 1450 children aged ≤24 months presenting with lower respiratory tract infections (LRTI) in outpatient settings between October 2021 and April 2023. Clinical data, detected pathogens via multiplex polymerase chain reaction, and follow-up data were collected. RESULTS:Among enrolled patients 19.7% tested positive for RSV. RSV-positive patients (RSV+) exhibited distinct clinical characteristics, including significantly higher proportions of wheezing, crackles, and tachypnoea than RSV-negative patients. Notably, we identified a previously unreported association between RSV infection and atopic conditions, with RSV+ patients demonstrating higher proportions of atopic eczema (odds ratio 1.65 [95% CI: 1.05-2.61]). 96.5% of all RSV+ patients received pharmacotherapy, predominantly beta-sympathomimetics, inhaled saline, and antipyretics. The mean recovery time was 12 days. CONCLUSION:In the outpatient setting, RSV infections during the first 2 years of life present with distinct clinical features and increased morbidity compared with other respiratory pathogens. The association with atopic conditions warrants further investigation. These findings characterize the considerable RSV burden in primary care before the implementation of immunization measures. TRIAL REGISTRATION:DRKS00026155.

BACKGROUND:Understanding infectious disease seasonality is crucial to inform immunization timing and risk communications. This study aimed to describe trends in respiratory syncytial virus (RSV) seasonality in Japan by determining thresholds across 47 prefectures using public health surveillance data. METHODS:Weekly RSV cases per sentinel (CPS) is the main indicator used in Japan. Data from approximately 3000 pediatric sentinel sites were extracted for 2012-2024. Seasonal, advisory, and alert thresholds were established via two globally utilized methods (moving epidemic methods [MEM] and fixed threshold method). Based on the established seasonal threshold, onset/duration was examined for each season during the study period. RESULTS:The fixed threshold method was finally chosen to establish the seasonal threshold, while medium and high-intensity thresholds under the MEM methods were chosen as advisory and alert thresholds. The threshold values were 0.23-0.80CPS for seasonal, 0.75-2.82CPS for advisory, and 1.11-4.20CPS for alert. The epidemic periods usually lasted less than 6 months, with distinct epidemic peaks in almost all prefectures over the 13-year observation. However, unlike other temperate countries/regions such as the United States and Europe, season onset shifted drastically from September-October in 2012/2013 to around March-April in 2024 with geographic variabilities. Calling season onset after 2 consecutive weeks above the threshold resulted in no false alarms in over half the prefectures. CONCLUSIONS:In countries such as Japan and the tropics/subtropics where the RSV seasons are less predictable, a flexible prevention strategy, tailored for each region/prefecture, using thresholds as guides, would ensure optimal protection against RSV and maximize public health benefits regardless of seasonal variability.

Parainfluenza virus (PIV) is a common cause of respiratory illness in children and immunocompromised adults, but little is known about its epidemiology or disease burden in the general adult population. This review evaluates published global epidemiological and disease burden for PIV in adults, including high-risk patients (immunocompromised or with chronic illnesses), and identifies existing data gaps. A PRISMA systematic review of publications from 2014 to 2023 in PubMed reporting PIV prevalence and disease burden (including hospitalisations, mortality) in adults (≥ 18 years) and high-risk patients was performed. Sixty-five studies were included; which skewed towards Asia, Europe, and North America, highlighting a data gap in global PIV prevalence. Overall prevalence of PIV (all strains) ranged from 0 to 15.2% [median 2%] in the general adult population (not considered high-risk but tested for infection). PIV3 was the most prevalent strain (0.6-15.2% [2.9]), followed by PIV4 (0.4-6.5% [1.9]), PIV1 (0.5-2.8% [1.1]), and PIV2 (0-2.9% [1.1]). PIV prevalence was generally higher in high-risk adults (up to 41% in certain risk groups) and those aged ≥ 65. Mortality rates ranged from 2 to 40% in those high-risk, while need for respiratory assistance ranged from 0.9% to 64.2% and hospitalisation from 3.7% to 45.3%. None of the studies reported cost-related healthcare resource utilisation. Variability of study designs, data stratification, and patient populations in the selected studies challenged evaluating the true prevalence of PIV and its burden. PIV infection carries an underappreciated burden, with substantial morbidity and mortality risks, especially in high-risk patients. Significant knowledge gaps exist regarding global prevalence and economic burden in the general adult population.

OBJECTIVE:To estimate the effectiveness of nirsevimab against respiratory syncytial virus (RSV)-associated acute otitis media (AOM) in ambulatory care. STUDY DESIGN:We conducted a test-negative design study, post hoc analysis using data from the prospective Oursyn study involving 37 primary care pediatricians across France from 2020 to 2025. Nasopharyngeal sampling for RSV was performed in infants younger than 1 year diagnosed with AOM during the first 2 RSV seasons with introduction of nirsevimab passive immunization (October 2023 to February 2024 and October 2024 to January 2025). The main outcome of the study was the detection of RSV status in infants with AOM. We performed a multivariable logistic regression with nirsevimab adjusted for age, sex, underlying chronic condition, prematurity, type of childcare, month, year, and geographic region of inclusion. Sensitivity analyses were performed as well. RESULTS:A total of 236 AOM events were included over the study period: 141 during the first season of nirsevimab implementation and 95 during the second season. Among infants with AOM, 41 (29.1%) and 15 (15.8%), respectively, tested positive for RSV. Nirsevimab-adjusted effectiveness was estimated to be 78.2% (95% CI 44.4-92.4) for the prevention of RSV-AOM in this sample. Sensitivity analyses found similar results. CONCLUSIONS:These findings highlight the broader protective effect of nirsevimab on complications of respiratory tract infections in infants. TRIAL REGISTRATION:NCT04743609.

Respiratory syncytial virus (RSV) is a leading cause of infant respiratory infections. The UK has implemented maternal vaccine to prevent RSV in infants from autumn 2024/5 whereas Spain implemented nirsevimab monoclonal antibody treatment in 2023/4 and 2024/5. The REACH study aimed to quantify the reduction in burden amongst infants of RSV-related hospital care across Spain and the United Kingdom (UK).Figure 1Cumulative RSV hospitalizations in infants <12 months of age (ICD-10 coded) up to 31-Jan-2025 This observational, retrospective, multi-center cohort study utilizes administrative and microbiology data from hospital sites in Spain and the UK, covering three consecutive RSV seasons from June 2022 to May 2025. Results are stratified by country, RSV season, patient risk groups, and age groups. The primary objective is to report by country the number of ICD-10 coded lower respiratory tract infection (LRTI) and RSV-LRTI hospital admissions, length of stay (LOS), and ICU admissions. Additional objectives include reporting laboratory-confirmed RSV-positive LRTI hospitalizations and estimating direct hospitalization costs, HCRU in the 30-day period post-discharge and concordance between ICD-10 and laboratory-test based diagnoses. Amongst infants < 12 months of age, the cumulative number of RSV hospitalizations, based on ICD-10 coded data, was reduced by 70.2% in Spain and 28.3% in the UK compared to the 22/23 (pre-prophylaxis) season, up until latest data cut-off (31-Jan-2022 vs. 31-Jan-2025). Amongst infants < 6 months of age, the reduction was 78.1% in Spain and 32.5% in UK. Amongst infants aged 13-24 months who did not benefit from prophylaxis, a similar trend with minimal change was observed in both countries, suggesting normal RSV circulation. Our preliminary results suggest substantial differences in the public health impact of the respective immunization campaigns targeting infants and pregnant women in Spain and UK. Data collection is ongoing, and full season results until end of May 2025 are expected by the time of ID week. Funding: Sanofi and AstraZeneca Oliver Martyn, MPH, Sanofi: Employee Rolf Kramer, PhD, Sanofi: Employee|Sanofi: Stocks/Bonds (Private Company) Karine Mari, MSc, Sanofi: Employee J. Jasper Deuring, PhD, Pfizer: Stocks/Bonds (Private Company) Saul N. Faust, FRCPCH PhD, AstraZeneca: Advisor/Consultant|AstraZeneca: Clinical trial investigator on behalf of institution|BioNTech SE: Funding of clinical trial to institution|CSL Seqirus: Advisor/Consultant|GSK: Clinical trial investigator on behalf of institution|J&J: Advisor/Consultant|J&J: Clinical trial investigator on behalf of institution|MedImmune: Advisor/Consultant|Merck: Clinical trial investigator on behalf of institution|Moderna: Honoraria|Moderna: Clinical trial investigator on behalf of institution|MSD: Advisor/Consultant|Novavax: Honoraria|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Pfizer: Clinical trial investigator on behalf of institution|Sanofi: Advisor/Consultant|Sanofi: Clinical trial investigator on behalf of institution|Valneva: Clinical trial investigator on behalf of institution

OBJECTIVES:This prospective surveillance study aimed to estimate the burden of laboratory-confirmed respiratory syncytial virus (RSV) in under 3-year-olds in the United Kingdom. SETTING:The study was implemented in Merseyside and Bristol, encompassing 11 primary care sites, 5 walk-in centres, 2 secondary care hospitals and 2 tertiary care hospitals. PARTICIPANTS:Children aged under 3 years presenting with lower respiratory tract infection (LRTI) symptoms were included, with a substudy in primary care recruiting children with upper respiratory tract infection (URTI). PRIMARY AND SECONDARY OUTCOME MEASURES:The primary outcome of the study was the prevalence of RSV infection in primary, secondary and tertiary healthcare settings. Secondary outcomes included severity outcomes (rates of hospitalisation and high dependency care admissions), risk factors for severe disease, economic burden of disease and coinfection prevalence. RESULTS:2000 children were included in the analysis (410 primary care and 1590 secondary/tertiary care). 318 were included in the URTI substudy. RSV prevalence was 50.0% (95% CI 46.7% to 53.3%) in children admitted to hospital via emergency departments (ED), 36.3% (95% CI 31.7% to 41.0%) in ED discharges, 36.5% (95% CI 24.7% to 49.6%) in primary care (LRTI) and 12.7% (95% CI 8.6% to 17.9%) in primary care URTI. Healthy term-born children accounted for 70.1% of RSV hospitalisations. Risk factors for severe disease included any level of prematurity, age <3 months and congenital cardiac disease. RSV-positive cases incurred a higher mean cost per participant (£1811, 95% CI £1720 to £1903) than RSV-negative cases (£1295, 95% CI £1220 to £1370). CONCLUSIONS:The findings revealed a substantial burden associated with RSV. Even moderate prematurity was a risk factor for severe disease, and these children may not benefit from maternal RSV vaccination due to missed late gestation antibody transfer. Furthermore, they would not be eligible for Nirsevimab under UK guidance, which supports consideration of broadening eligibility to include these children.

Summary Background Respiratory syncytial virus (RSV) is one of the main causes of morbidity in infants and young children worldwide. Current data on RSV-associated disease burden in Germany before the introduction of new immunization strategies is lacking. Methods The PAPI study is a multicenter, prospective surveillance study of lower respiratory tract infections (LRTI) in children aged ≤ 24 months in Germany. Results Data from 1607 children with LRTI hospitalized in twelve German hospitals between September 2021 and May 2023 were analyzed. Among these children, RSV was the most frequently detected pathogen (57.1%), followed by rhino/entero-, metapneumo- and parainfluenza virus. Children with RSV were significantly younger than those with LRTI of other causes (mean of 5.6 ± SD 6.1 vs. mean of 10.1 ± SD 7.3 months, p < 0.001) and more frequently affected in their first six months of life. RSV positive children were significantly more likely to develop hypoxemia (61.9% vs. 44.3%, p < 0.001) and need for intravenous or enteral fluid supplementation (48.1% vs. 43.1%, p = 0.009; 13.2% vs. 5.9%, p < 0.001) than those without RSV. Conclusion RSV is the dominant pathogen for LRTI-associated hospitalizations in children ≤ 24 months in Germany and associated with a particularly high need for treatment. The ongoing implemented use of RSV immunization according to current recommendations could lead to significant reduction in early childhood morbidity in Germany.

Abstract Background Respiratory syncytial virus (RSV) is a leading cause of respiratory tract infections and hospitalizations among infants worldwide. In 2023, the universal RSV immunization of all infants with the novel monoclonal antibody nirsevimab was introduced in several countries. This systematic review aims to summarize early real-world evidence on achieved immunization rates as well as on the impact and effectiveness of nirsevimab prophylaxis among infants. Methods A systematic literature search for full-text publications was conducted in the databases PubMed and Embase. The review included observational studies that investigated the impact or effectiveness of nirsevimab in routine use. Clinical research, decision analytic modeling studies, and studies describing the disease burden of RSV without direct reference to nirsevimab use were excluded. Results Five studies fulfilled the inclusion criteria, including one from the United States (US), one from Luxembourg, and three studies from different regions in Spain. Population-wide immunization rates were reported in Luxembourg and several Spanish regions, all exceeding 80%. Four studies estimated the effectiveness of nirsevimab in preventing RSV-related hospitalizations, including two population-based cohort studies and two case-control studies. The effectiveness of nirsevimab in preventing RSV-related hospitalizations was calculated at 88.7% (95%-CI: 70-96), 84.4% (95%-CI: 77-90), and 82.0% (95%-CI: 66-90) in the Spanish studies and 90% (95 %-CI 75-96) in the US. While no effectiveness estimate was reported in Luxembourg, the number of RSV-related hospitalizations among infants under 6 months decreased by 69% after nirsevimab introduction compared to the same period of the previous year. Conclusion High uptake was observed in both Luxembourg and Spain. Despite methodological differences between studies and varying implementation strategies between countries, observed effects of recommending nirsevimab to all infants were largely consistent. International evidence suggests that nirsevimab substantially reduces RSV-related hospitalizations and thus relieves the burden on healthcare systems during the RSV season. Disclosures Moritz Wick, MSc, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company) Anna C. Meyer, PhD, Sanofi: Employee Oliver Damm, PhD, Sanofi: Employee Annika Wülfing, PhD, Sanofi: Employee and may hold stocks Oliver Martyn, MPH, Sanofi: Employee of Sanofi|Sanofi: Stocks/Bonds (Public Company) Rolf Kramer, PhD, Sanofi: Employee of Sanofi|Sanofi: Stocks/Bonds (Public Company)

Abstract Background The objective of this systematic review was to evaluate the scope of published epidemiological and patient outcomes data available for parainfluenza virus (PIV) in adults worldwide and to identify data gaps for this patient population. Methods PubMed was searched for original articles on epidemiology or patient outcome of PIV (any strain) published from January 1, 2014, to August 26, 2023. This identified 549 publications. Studies were screened for relevant data in adults and in those at high risk for respiratory infections (severe pulmonary diseases, malignancies, transplants, cystic fibrosis, or those who were unhoused). Based on an initial screen, 390 articles were excluded, yielding 166 articles for full text review (Figure). This included 7 studies identified by screening bibliographies of excluded review articles that were not captured by the initial search. Upon review, 103 further articles were excluded (eg, study time frame was before 2014 or during the COVID-19 pandemic, lack of PIV or target data reported in adults). Collectively, this process identified a database of 63 articles for final analysis with any epidemiological or outcome data. Results The prevalence of PIV reported in the literature varied widely based on geography and patient population. The population was broad including hospitalized adults, healthy volunteers, and those presenting with respiratory infections. Patients were defined as “otherwise healthy” if they were not considered high risk. Preliminary results indicate the overall prevalence of PIV (PIV1-4 or PIV unspecified) ranges from 0-15.2% [median 2%] in otherwise healthy adults, with PIV3 as the most prevalent (0.6-15.2% [2.9]) followed by PIV4 (0.4-5.9% [0.5]), PIV1 (0.5-2.8% [1.1]), and PIV2 (0-2.9% [1.1]). The prevalence of PIV was higher in at-risk adults (up to 52%). Patient outcome data was scarce, with mortality rates being the most frequently reported topic. Hematopoietic stem cell transplant patients were found to be the most at risk for PIV-associated mortality, though there was no clear strain-specific pattern of mortality given the limited data on patient outcomes. Conclusion Significant data gaps remain on the burden of PIV on adults, particularly in otherwise healthy adults. Disclosures Oliver Martyn, MPH, Sanofi: Employee of Sanofi|Sanofi: Stocks/Bonds (Public Company) Peter Openshaw, PhD, AstraZeneca: Advisor/Consultant|AstraZeneca: Honoraria|AstraZeneca: Speaker bureau participation|CSL Seqirus: Advisor/Consultant|CSL Seqirus: Honoraria|GSK: Advisor/Consultant|GSK: Honoraria|Icosavax: Advisor/Consultant|Janssen: Advisor/Consultant|Janssen: Honoraria|Medical Research Council UK: Grant/Research Support|Medscape: Speaker bureau participation|Moderna: Advisor/Consultant|Moderna: Honoraria|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Grant/Research Support|Sanofi: Speaker bureau participation Clemens Vlasich, MD, MSc, Sanofi: Employee of Sanofi|Sanofi: Stocks/Bonds (Public Company) Rolf Kramer, PhD, Sanofi: Employee of Sanofi|Sanofi: Stocks/Bonds (Public Company)

Regarding nirsevimab immunization status, among 1085 infants hospitalized for bronchiolitis, the odds of hospitalization for respiratory syncytial virus bronchiolitis were 4.7 times higher for nonimmunized children. Immunized infants were less likely to require oxygen supplementation (20.2% vs. 30.6%, P = 0.02) and had a 1-day shorter hospital stay. Respiratory syncytial virus bronchiolitis was less frequent and less severe in infants immunized with nirsevimab.

BACKGROUNDRespiratory syncytial virus (RSV) is a major cause of morbidity in older adults.AIMWe aimed to investigate the epidemiology of RSV in adults in five European countries and one region before and during the COVID-19 era.METHODSWe conducted a retrospective analysis using national hospital admission data from Denmark, England, Finland, the Netherlands, Scotland and regional prospective surveillance data from the Spain-Valencia region. We included patients aged ≥ 18 years hospitalised for respiratory tract infections (RTIs) 2016-2023 and assessed RSV-coded and laboratory-confirmed hospitalisations, intensive care unit (ICU) admissions and mortality.RESULTSHospitalisations associated with RSV varied by country and year but increased with increasing age regardless of the use of RSV-coded or RSV-confirmed data, the country or year. The highest hospitalisation rates were in patients aged ≥ 85 years. We found that RSV-coded hospitalisations underestimated the case numbers when compared with laboratory-confirmed cases by an average of 1.9 (standard deviation (SD): ± 0.9). Admissions to ICU associated with RSV in England and CFR in England and Finland displayed different patterns post-COVID-19 pandemic peak but were not notably higher compared with RTI admissions.CONCLUSIONOur findings reveal a consistency of RSV hospital admission patterns between European countries in the study period, with higher incidence rates among older patients. The differences between the numbers of RSV-coded and laboratory-confirmed cases highlight the critical need for improved surveillance, diagnostic practices and coding guidelines to better assess the incidence. Our findings could be vital for guiding public health strategies, particularly with the introduction of RSV vaccines for older adults.

As part of the NIRSEGAL study ( https://www.nirsegal.es/en ), we present the clinical characteristics and course of respiratory syncytial virus (RSV)-related low respiratory tract infection (LRTI) hospitalizations in infants eligible for nirsevimab administration during the 2023–2024 season. Infants eligible for nirsevimab immunization (born between 1 April, 2023, and 30 March, 2024) who were hospitalized due to RSV-related LRTI between September 25, 2023, and April 15, 2024, in a hospital from the Galician Public Health system were included. Clinical and demographic characteristics of RSV-related LRTI hospitalizations were analyzed, with comparisons made between breakthrough cases (those immunized with nirsevimab) and non-breakthrough cases. During the study period, 69 RSV-related LRTI hospitalizations were recorded, with a median hospital stay of 4 (interquartile range (IQR) 3–6) days; 65.2

OBJECTIVES:Respiratory syncytial virus (RSV) is a substantial cause of hospital admission in young children and leads to seasonal pressure on pediatric emergency units in most countries. This study aims to assemble national or large-scale data on RSV hospitalisations from six European countries with a standardised approach to provide recent burden data for all children and assess changes since SARS-CoV-2's emergence. METHODS:We analysed 2016-2023 hospital records from national registries in Denmark, England, Finland, The Netherlands, and Scotland, and from a hospital surveillance network in Spain-Valencia for children below 18 years. We considered separately RSV-coded and RSV laboratory-confirmed cases, comparing them to respiratory tract infections. We studied the temporal evolution of incidence rates and case reporting practices, comparing pre- and post-COVID-19 periods. RESULTS:Post-COVID-19 observed RSV hospital burden was similar to the pre-COVID-19 one for younger children but higher for the 1-2 years, 3-4 years, and 5-17 years age groups. No change in terms of coding-neither diagnosis nor RSV-coding when RSV was laboratory-confirmed-was detected. CONCLUSIONS:Hospital RSV burden in children is significant but currently not fully monitorable. Further efforts to harmonise coding practices both within and across countries would improve the quality of future analyses. Additional data in future seasons should complement current outcomes to inform decisions regarding RSV prevention.

We previously reviewed methods for estimating the timing of respiratory syncytial virus (RSV) epidemics. This study examines the impact of various estimation methods on determining the start, end, duration, and capture rate of RSV epidemics. We applied eight estimation methods to RSV surveillance data from the Global Epidemiology of RSV (GERi) study, covering Chile, New Zealand, Singapore, South Africa, Spain, and the United States: 3% and 10% positivity rate, moving epidemic method (MEM), mean positivity, 1.2% total detections, mean and 60% mean number, and 75% average annual percentage (AAP). We compared the median start, end, duration, and capture rate of RSV epidemics obtained from these methods. Within countries, the median duration of RSV epidemics varied by over 10 weeks, and the median capture rates ranged from > 95 to < 60%, depending on the estimation method. Generally, the 3% positivity rate method identified the longest RSV epidemics (earliest median start and latest end, and highest capture rate). The 10% positivity rate, MEM, and 75% AAP methods indicated the shortest RSV epidemics with the lowest capture rate. The remaining four methods produced intermediate results. These findings underscore the importance of selecting estimation methods suited to the surveillance system and the intended use, whether for outbreak alert, planning, or targeted interventions.

Importance:New resistant mutations of respiratory syncytial virus type B (RSV-B) have been observed during the first year of implementation nirsevimab treatment. During the second season of implementation of nirsevimab treatment in France, RSV-B was predominant. Objectives:To assess and compare the effectiveness of nirsevimab treatment in preventing RSV bronchiolitis in pediatric emergency departments during the first and second seasons of implementation of treatment in France. Design, Setting, and Participants:This a multicenter test-negative case-control study included 636 infants younger than 1 year who received a diagnosis of a first bronchiolitis episode in 5 pediatric emergency departments in France during the 2 first seasons of implementation of nirsevimab treatment (from October 5, 2023, to February 29, 2024, and from October 15, 2024, to January 31, 2025) and underwent a nasopharyngeal test for RSV. Main Outcomes and Measures:The main outcome of the study was the RSV status of the bronchiolitis cases. Multivariable logistic regression was performed with nirsevimab as the explanatory variable, adjusted on age, sex, risk factors of bronchiolitis, type of childcare, month, and center of inclusion. Effectiveness was calculated for each season and compared using the likelihood ratio test. Subgroup analysis by age and severity as well as sensitivity analyses were performed. Results:The study included 636 patients with bronchiolitis (median age, 3.0 months [IQR, 1.4-5.0 months]; 333 boys [52.4%]). In both seasons, 162 of 636 patients (25.5%) were immunized with nirsevimab. During the first season of implementation, 273 of 384 patients (71.1%) tested positive for RSV; during the second season, 181 of 252 patients (71.8%) tested positive for RSV. The effectiveness of nirsevimab treatment against RSV bronchiolitis was estimated to be 83.2% (95% CI, 68.0%-91.4%) during the first season and 89.3% (95% CI, 77.8%-95.1%) during the second season; no statistically significant difference in effectiveness was found between the 2 seasons (P = .97). Subgroup and sensitivity analyses provided similar results. Conclusions and Relevance:In this test-negative case-control study of nirsevimab treatment, its effectiveness in reducing pediatric emergency department visits for RSV bronchiolitis during the second season of national immunization was high and comparable with that observed in the first season. Although RSV-B resistant strains had been recently identified, it did not appear to have important clinical consequences to date. Continued close monitoring of RSV epidemiology in the context of the widespread nirsevimab use remains essential.

Background The majority of respiratory syncytial virus (RSV) infections in young children are managed in primary care, however, the disease burden in this setting remains poorly defined. Methods We did a prospective cohort study in primary care settings in Belgium, Italy, Spain, the Netherlands, and the UK during the RSV seasons of 2020-21 (UK only; from Jan 1, 2021), 2021-22, and 2022-23. Children aged younger than 5 years presenting to their general practitioner or primary care paediatrician with symptoms of an acute respiratory tract infection were eligible for RSV testing. Children who tested positive for RSV were consented and followed up for 30 days via a physician clinical report (initial primary care visit on day 1) and two parent-report questionnaires (days 14 and 30). We assessed the burden of RSV in terms of clinical course (symptoms, illness duration, and complications), health-care resource utilisation (primary care visits, emergency department visits, hospitalisation rate, and medication use), and societal impact (daycare or school absence and parental work absence) for the 30-day follow-up period. Findings Among 3414 tested children, 1124 (32.9%; 95% CI 31.3-34.5) tested positive for RSV. Among children with data on age, RSV positivity rate was 38.9% (36.1-41.7; n=466 of 1198) in children younger than 1 year and 25.9% (24.0-27.9; n=513 of 1979) in those aged 1 to <5 years. Of the 1124 RSV-positive children, 878 (78.1%) were enrolled and had day 1 data collected (median age 11.1 months [IQR 6.0-22.0]; 446 [50.9%] boys and 431 [49.1%] girls [N=877]). RSV illness lasted a mean of 11.7 days (95% CI 11.2-12.2; n=794). At day 14 and day 30, any remaining symptoms were reported in 451 of 804 (56.1% [95% CI 52.6-59.6]) and 261 of 724 (36.0% [32.6-39.7]) children. The mean number of primary care visits per child ranged from 1.4 (95% CI 1.2-1.6; the Netherlands) to 3.0 (2.8-3.3; Spain), and was higher in children younger than 1 year (2.7 visits [2.4-2.9]) than in those aged 1 to <5 years (2.1 [1.9-2.2]). Prescribed medication use varied, from 25 of 96 children (26.0% [95% CI 17.6-36.0]; the UK) to 228 of 297 children (76.8% [71.5-81.5]; Italy), with bronchodilators and antibiotics being the most commonly prescribed medicines across all countries. Prescribed medication use was reported in 258 of 418 children aged 1 to <5 years (61.7% [56.9-66.4]) and 196 of 394 children younger than 1 year (49.7% [44.7-54.8]). Missed working days by parents due to their child's RSV illness were reported in 340 of 744 cases (45.7% [42.1-49.4]); the mean number of missed workdays ranged from 1.3 days (95% CI 0.5-2.2) in Spain to 4.1 days (3.3-5.0) in Belgium. Interpretation RSV infections in children younger than 5 years in primary care are associated with substantial symptomatology, health-care utilisation, and parental work absence. Notable differences in RSV burden existed across countries, likely due to differences in primary health-care systems, clinical practice, and health-care-seeking behaviour. This study emphasises the importance of considering country-specific primary care burden estimates when considering the implementation of RSV immunisations programmes. Copyright (c) 2025 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.

Bronchiolitis is one of the leading reasons for paediatric emergency department (PED) visits. France was one of the few countries in the world to implement nirsevimab during winter 2023–2024 in order to reduce the burden of bronchiolitis each year. We conducted a test-negative design study, including all infants younger than 1, diagnosed with a first episode of bronchiolitis. We included all cases presenting to the PED of five university hospitals across France, between October 1, 2023, and February 29, 2024, and undergoing a nasopharyngeal sample for RSV testing. Case patients were the RSV-positive bronchiolitis and control patients the RSV-negative. As a follow-up, all parents were contacted by e-mail 15 days after inclusion. We included 383 bronchiolitis patients, of which 274 tested positive for RSV (75.2