Global, regional, and national disease burden estimates of acute lower respiratory infections due to respiratory syncytial virus in young children in 2015: a systematic review and modelling study

Health economic evaluation of implementing a universal immunization program with nirsevimab compared to standard of care for the prevention of respiratory syncytial virus disease in Canadian infants

Respiratory syncytial virus (RSV) is a highly contagious pathogen and a leading cause of severe lower respiratory tract illness (LRTI) in infants and young children, irrespective of risk factors. Nirsevimab, an extended half-life monoclonal antibody, was approved in Canada in 2023 as a passive immunizing agent for the prevention of RSV LRTI. This study evaluated the optimal price per dose (PPD) at commonly accepted willingness-to-pay (WTP) thresholds among Canadian infants compared to the current standard of care (i.e. palivizumab for preterm infants and those with specific medical conditions). A static decision tree model was developed to assess the impact of nirsevimab on RSV-related health and economic outcomes among Canadian infants - including outpatient physician and emergency department visits, inpatient hospitalizations including intensive care unit (ICU) admissions and mechanical ventilation, and the associated healthcare costs of these outcomes. The model utilized Canadian epidemiological and cost inputs where possible, adopting a societal perspective. Compared to the standard of care, nirsevimab was expected to prevent 47,609 RSV-related health events, including 2,296 hospitalizations and a reduction of approximately $45 million in direct healthcare costs. At a WTP threshold of $50,000 per quality-adjusted life-year (QALY), the estimated base case PPD was $536, based on average cost assumptions across several costing scenarios. These findings suggest that universal immunization with nirsevimab could significantly reduce the health and economic burden of RSV among Canadian Infants.

Severity and outcomes of adult respiratory syncytial virus inpatient compared with influenza: observational study from Japan

BACKGROUND

Respiratory syncytial virus (RSV) significantly impacts not only children but also adults. However, knowledge of the severity and outcomes among adult RSV inpatients is still limited.

OBJECTIVES

To clarify the short- and long-term health threats associated with adult RSV infections.

METHODS

This retrospective observational study included 56,980 adult inpatients aged 18 years and older due to RSV or influenza infection between April 2010 and March 2022. After inverse probability weighting adjustment, we used Poisson's regression to estimate the risk of outcomes.

RESULTS

The RSV group had a higher risk of requiring mechanical ventilation during hospitalization compared to the influenza group (9.7% vs. 7.0%; risk ratio (RR), 1.35; 95% confidence interval (CI), 1.08-1.67). In-hospital mortality was comparable between RSV and influenza groups (7.5% vs. 6.6%; RR, 1.05; 95% CI, 0.82-1.34). RSV group was associated with increased risk of readmission within 1 year after surviving discharge (34.0% vs. 28.9%; RR, 1.19; 95% CI, 1.07-1.32) and all-cause mortality within 1 year of admission (12.9% vs. 10.3%; RR, 1.17; 95% CI, 1.02-1.36). In the age-stratified analysis, the RSV group aged 60 years and older had a higher risk than the influenza group for in-hospital death, readmission and all-cause mortality within one year.

CONCLUSIONS

RSV infections demonstrated comparable or greater health threats than influenza infections not only during hospitalization but also in long-term outcomes. The findings underscore the threat of RSV in adults, the impact on healthcare systems and the need for continued development of public health counter measures against RSV.

Cost-savings and health impact of strategies for prevention of Respiratory Syncytial Virus with nirsevimab in Chile based on the integrated analysis of 2019-2023 national databases: A retrospective study

BACKGROUND

In the latter half of 2023, the northern hemisphere initiated the rollout of nirsevimab immunization strategies for infants, yielding promising early results. As Chile prepared for its 2024 strategy implementation, we retrospectively evaluated the potential cost-saving nature of various immunization strategies.

METHODS

Leveraging comprehensive inpatient, outpatient, and sentinel programs data, we conduct a simulation-based retrospective analysis to evaluate the net cost savings of various immunization strategies based on nirsevimab. We first characterize RSV burden among Chilean infants between 2019 and 2023, focusing on medically attended lower respiratory tract infections (MA LRTI), hospital admissions (HA LRTI), and severe cases requiring ICU admission (ICU LRTI). Utilizing nirsevimab efficacy estimates, we simulate counterfactual scenarios to estimate reductions in outpatient visits, hospitalizations, and ICU admissions had nirsevimab been used. We evaluate diverse immunization strategies and estimate their cost-saving status.

FINDINGS

With nirsevimab costing about USD$225 per dose, immunizing infants under 6 months before the RSV season, all newborns during the season, and high-risk groups would have been cost-saving in 2023 and 2019. This strategy would have significantly decreased the strain on the healthcare system during the seasonal surge, reducing 13,533 ICU (77·81/1000 live newborns) and 27,465 hospital bed requirements (157·91/1000 live newborns), alongside 46,886 emergency room visits (269·58/1000 live newborns).

INTERPRETATION

In Chile, a country with a GDP per capita of USD$17,000, various immunization strategies are cost-saving for scenarios comparable to pre-pandemic 2019 and to the particularly severe 2023 when considering only those direct costs associated with patient care, albeit differing in their impact in health outcomes. The resulting decrease in healthcare strain during the Winter virus surge underscores the strategy's impact.

Comparative analysis of acute respiratory infections of viral etiology in children under 6 months with and without nirsevimab in the Balearic Islands (2022-2023 and 2023-2024)

INTRODUCTION

Since 2023, a monoclonal antibody (nirsevimab) specifically directed against the preF form of RSV has been marketed in Spain. The impact of late immunization in the population <6 months as a cause of other respiratory infections requiring a hospital visit has been analyzed.

MATERIAL AND METHODS

The viral etiology of acute respiratory infections (ARIs) diagnosed in the 2022-2023 and 2023-2024 seasons has been prospectively compared, and in this last season between recipients and non-recipients of nirsevimab. Global provisional coverage was 77% of the population.

RESULTS

In the 2022-2023 season, 303 < 6 months with an ARI were detected, while in the 2023-2024 season there were 278 minors (19% less). The positivity in the first season was 79.9% compared to 70.5% in the current season. A significant difference has been observed in the detection of RSV between both groups and a decrease of 82.9% of cases in the current season. Of the 278 cases <6 months detected in the 2023-2024 season, 192 (69.1%) received immunization with nirsevimab and 86 (30.9%) did not receive it. The percentage of positivity in those immunized was 69.3%, compared to 73.3% in those not immunized. Significant differences have been observed in the detections of RSV and influenza between both groups.

CONCLUSIONS

Immunization at <6 months with nirsevimab has shown a significant reduction in RSV infections compared to the previous season. It does not seem, however, that it can reduce infections by other respiratory viruses.

Evaluation of the costs of care for pediatric patients hospitalized for RSV: A retrospective cohort study in Belgium

INTRODUCTION

This study aimed to evaluate the costs of respiratory-syncytial virus (RSV)-related hospitalizations in children under 3 years old in Belgium for hospitals and health insurance, and to identify factors influencing costs.

METHODS

This retrospective cohort study used data from 16 French-speaking hospitals in Belgium, covering January 1, 2018, to December 31, 2019. RSV diagnoses for children under three were identified using International Classification of Diseases-Tenth Revision (ICD-10) codes, resulting in 2176 hospitalizations analyzed for cost assessment. Hospital and health insurance costs were derived from administrative and billing data, adjusted for inflation, and analyzed using descriptive and inferential statistics, including regression models to assess cost factors.

RESULTS

Of the 2176 RSV-related hospitalizations, 61.8 % were in children under one year, and 74.1 % had readmissions within a year. The median length of stay (LOS) was 3.67 days, with a median hospital cost of €2924 and a median health insurance cost of €2221 per stay. Factors associated with higher costs included longer LOS, severe diagnosis-related group category, pediatric intensive care unit admission, and non-invasive ventilation use, with costs generally lower for children aged 1-2 years. Based on these data, the annual costs in Belgium associated with RSV hospitalizations in the pre-immunization era are estimated to exceed €26 million from the health insurance perspective and €29 million from the hospital perspective.

CONCLUSION

This study highlights the significant and underestimated financial burden of RSV hospitalization in Belgium. This emphasizes the need for better resource allocation to reduce the economic impact of RSV on healthcare systems.

Genetic Diversity in the Fusion Gene of Respiratory Syncytial Virus (RSV) Isolated From Iraqi Patients: A First Report

Molecular evaluation of the respiratory syncytial virus (RSV) genome is one of the common strategies applied to understand the viral pathogenicity and control its spreading. In this study, we carried out molecular evaluation on the targeted fusion (F) gene region in the RSV-positive samples of Iraqi patients during the autumn and winter of 2022/2023. One hundred and fifty patients with lower respiratory tract infections were screened for RSV using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Sanger sequencing was performed on the RSV-positive samples targeting 1061 nucleotides (from nucleotide 6168 to 7228 within the RSV genome) and 1000 nucleotides (from nucleotide 6122 to 7121 within the RSV genome) of the F gene region for RSV-A and RSV-B, respectively. The results showed some nucleotide changes within the targeted F gene, which were grouped in distinct clade, closely related to isolates from Austria, Argentine, Finland, and France through phylogenetic analysis. In silico protein modeling using the SWISS-MODEL and I-TASSER web tools based on nonsynonymous changes of amino acid sequence showed some good-predicted models that can be utilized for antiviral screening. In summary, the identified nucleotide variations in the F gene could influence vaccine development as the F protein is the primary target for the major antigen of RSV. Molecular surveillance data of RSV local isolates are also essential for studying new genomic changes and enable the prediction of potential new antiviral agents.

Cost-Effectiveness and Public Health Impact of Universal Prophylaxis with Nirsevimab Against Respiratory Syncytial Virus (RSV) Infections in all Infants in Japan

INTRODUCTION

Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract disease, and the standard prevention strategy in Japan is limited to high-risk infants. Nirsevimab provides protection against medically attended (MA) RSV infection in healthy late-preterm and term infants and was approved in Japan in 2024. This study estimates the cost-effectiveness of universal immunization with nirsevimab in an all-infant population from the Japanese public healthcare payer perspective.

METHODS

A static decision analytic model, able to track costs and health outcomes in a cohort of infants, was adapted to the Japanese setting. The standard of care, palivizumab, administered to high-risk infants, was compared with nirsevimab administrated to all infants in the first year, and an additional increased dose of nirsevimab (200 mg) in the second season for high-risk infants. Differences in costs and quality-adjusted life years (QALYs) were captured considering RSV-related MA health events requiring inpatient hospitalizations, emergency room visits, and primary care visits, as well as RSV-related complications. Sensitivity and scenario analyses were conducted to explore the robustness and uncertainty of the study.

RESULTS

Assuming a price of ¥45,000 for nirsevimab, universal immunization with nirsevimab was found to be cost-effective with an incremental cost-effectiveness ratio (ICER) of ¥4,537,256/QALY. At the Japanese willingness-to-pay threshold of ¥5,000,000, the economically justifiable price was ¥45,496. Using the societal perspective, the ICER decreased to ¥1,695,635/QALY. Nirsevimab has a substantial public health impact on RSV disease burden, reducing approximately 50% of RSV-associated health events in an all-infant population.

CONCLUSION

The analysis demonstrated that universal prophylaxis strategy with nirsevimab would significantly reduce the health and economic burden associated with RSV among infants in Japan. At the assumed price, nirsevimab can provide a cost-effective prophylaxis option against RSV infection in an all-infant population not limited to infants born prematurely or with high risk.

Genotypic analysis of rhinovirus and human respiratory syncytial virus in sudden unexpected death in infancy cases at Tygerberg Hospital, Cape Town, South Africa

Infant mortality remains a major global concern. Sudden unexpected death in infancy (SUDI) is reported globally and an infant mortality rate of 23.129 per 1 000 live births has been reported in the Western Cape, South Africa, in 2024. Infections are often confirmed in SUDI cases admitted to the Tygerberg Medico-legal Mortuary in Cape Town, but molecular diversity in respiratory viruses is underreported. A total of 162 previously confirmed polymerase chain reaction (PCR)-positive trachea and / or lung samples from SUDI cases collected between 2015 and 2019 were retested for either rhinovirus or human respiratory syncytial virus (RSV). Sixty-four samples were positive for rhinovirus and 15 for RSV. Results from 5 of all positive samples were outside the PCR assay amplification limits determined by the cycle threshold (Ct) value and were excluded. Another 4 samples did not amplify, and the remaining 70 underwent subsequent sequencing, but successful sequences could only be obtained in 53 samples. All three rhinovirus (A, B and C) genotypes were identified, with RV-A most prevalent, followed by RV-C and RV-B. RSV-A and RSV-B were detected equally, and after amino acid alignment, 20 amino acid duplication and nine substitutions were found that confirmed two RSV-BA9 genotypes. This study describes the molecular and phylogenetic characterisation of specific respiratory viruses in SUDI cases in South Africa. However, the rapid decline in viral viability in post-mortem samples does not allow correlation between viral genotypes and cause of death or disease severity. Future prospective studies should therefore investigate temporality and associations between specific viral strains and clinical disease severity and mortality.

Utilizing Infectious Disease Surveillance for Epidemic Warnings of Respiratory Syncytial Virus Infections in Japan from 2015 to 2019

Japan's National Epidemiological Surveillance of Infectious Diseases (NESID) has implemented a warning system for detecting epidemics in smaller districts, such as public health center (PHC) areas. This system is applied to influenza and pediatric infectious diseases. Respiratory syncytial virus (RSV) infection is not included but its incorporation is needed for effective early epidemic detection. We aimed to propose criterion values for an epidemic warning system related to RSV infection within PHC areas. We analyzed the weekly number of RSV infection cases reported by sentinel medical institutions (SMIs) in the NESID from 2015 to 2019. Weekly cases per SMI in the PHC area were set to establish an index for epidemic warnings. We determined criteria for issuing an epidemic warning by identifying distribution percentiles within the index. Setting the critical values for the onset and end of the epidemic warning at 5 and 2, respectively, yielded an approximately 5% annual proportion of PHC areas with an epidemic warning, which aligns with previously accepted frequency criteria for epidemic warnings. The 5-year (2015-2019) RSV infection epidemic trend showed that the set critical values were appropriate. Using these values could assist with issuing warnings regarding potential RSV infection epidemics in Japan.

Clinical diagnostic value of throat swabs in pediatric acute lower respiratory tract infections using targeted next-generation sequencing

BACKGROUND

To evaluate the clinical utility of targeted next-generation sequencing (tNGS) for pathogen detection of pediatric acute lower respiratory tract infections (ALRTIs), with a particular focus on the use of throat swab samples.

METHODS

In this diagnostic accuracy study involving 132 children, throat swabs and bronchoalveolar lavage fluid (BALF) samples were collected and analyzed by tNGS, and the results were compared with those obtained from conventional diagnostic methods. The impact of prior antibiotic use on the detection rate of tNGS was evaluated, the consistency between throat swabs and BALF was assessed, and the economic cost and invasiveness of the sampling methods were examined.

RESULTS

This study enrolled 132 children, of whom 79 (60%) were boys and 53 (40%) were girls. Ninety-two (70%) of the patients had fever, and 128 (97%) had a cough. The detection rates of bacteria, viruses, and atypical pathogens in BALF samples by tNGS were 89.5% (n = 68), 98.2% (n = 108), and 77.8% (n = 63), respectively. Compared to traditional detection methods, tNGS showed significantly higher detection rates for bacteria and viruses (P < 0.001), but there was no statistically significant difference in the detection of atypical pathogens (P = 0.59). The use of antibiotics had no significant effect on bacterial detection by tNGS (P = 0.237). Using BALF-tNGS as the "gold standard," the sensitivities of tNGS of throat swabs for detecting bacteria, viruses, and atypical pathogens were 95.83%, 88.16%, and 92.06%, respectively, with specificities of 55.95%, 83.93%, and 100%. In the analysis of economic costs and invasiveness, the cost of throat swab sampling was significantly lower than that of BALF sampling, and the associated pain score and complication rate were significantly lower (P < 0.05).

CONCLUSIONS

tNGS with throat swabs offers higher sensitivity and specificity than traditional methods for diagnosing pediatric ALRTIs. As such, it offers a less invasive, more cost-effective alternative to BALF sampling.

Intestinal-pulmonary axis: a 'Force For Good' against respiratory viral infections

Respiratory viral infections are a major global public health concern, and current antiviral therapies still have limitations. In recent years, research has revealed significant similarities between the immune systems of the gut and lungs, which interact through the complex physiological network known as the "gut-lung axis." As one of the largest immune organs, the gut, along with the lungs, forms an inter-organ immune network, with strong parallels in innate immune mechanisms, such as the activation of pattern recognition receptors (PRRs). Furthermore, the gut microbiota influences antiviral immune responses in the lungs through mechanisms such as systemic transport of gut microbiota-derived metabolites, immune cell migration, and cytokine regulation. Studies have shown that gut dysbiosis can exacerbate the severity of respiratory infections and may impact the efficacy of antiviral therapies. This review discusses the synergistic role of the gut-lung axis in antiviral immunity against respiratory viruses and explores potential strategies for modulating the gut microbiota to mitigate respiratory viral infections. Future research should focus on the immune mechanisms of the gut-lung axis to drive the development of novel clinical treatment strategies.

Exploring the Contribution of TLR7 to Sex-Based Disparities in Respiratory Syncytial Virus (RSV)-Induced Inflammation and Immunity

TLR7 plays a key role in recognizing viral RNA to initiate an immune response. Sex-based differences in the severity of RSV respiratory infections have been noted, and this may be related to higher expression of X-linked toll-like receptor 7 (TLR7) in female immune cells. Indeed, TLR7 has been shown to influence sex differences in responses to other respiratory viruses; however, its role in RSV infection remains underexplored. We infected adult C57Bl/6 or TLR7 knockout mice with RSV and compared the specific lung immune responses between different sexes. Gene expression analysis revealed that infected female mice had elevated levels of type I and II interferons, proinflammatory cytokines, chemokines, and viral transcripts in their lungs compared to males. Additionally, females exhibited increased numbers of macrophages and higher antibody responses in the airways. Deletion of TLR7 diminished the sex differences in certain cytokine and antibody responses. Furthermore, ex vivo infection of male alveolar macrophages with RSV resulted in greater production of proinflammatory cytokines and viral transcripts than in female macrophages, suggesting inherent sex differences in macrophage responses. These findings provide new insights into the mechanisms underlying sex differences in RSV pathophysiology and suggest that TLR7 contributes to an enhanced inflammatory response in females.

Advancements in the application and research of baculovirus vector vaccines for respiratory diseases in human

The rapid spread of respiratory diseases, such as influenza, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), Middle East Respiratory Syndrome Coronavirus (MERS-CoV), and Respiratory Syncytial Virus (RSV), poses significant challenges to global public health systems. Vaccination remains the most effective strategy to mitigate these threats. Baculovirus Expression Vector Systems (BEVS) have emerged as a promising platform for vaccine development, addressing key limitations of traditional methods, including complex production processes, lengthy timelines, and high costs. BEVS offers distinct advantages, such as enhanced efficacy, safety, cost-effectiveness, and scalability for large-scale manufacturing. This review highlights the application of BEVS in combating respiratory diseases by analyzing preclinical studies, clinical trials, and approved vaccines targeting these pathogens. It also examines recent advancements in BEVS technology, emphasizing its capacity to accelerate vaccine development and respond to emerging respiratory threats. By focusing on the synergy between BEVS and respiratory disease prevention, this review provides valuable insights to guide global vaccine innovation.

Structures of respiratory syncytial virus G bound to broadly reactive antibodies provide insights into vaccine design

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease in infants and older adults. The attachment glycoprotein (RSV G) binds to the chemokine receptor CX3CR1 to promote viral entry and modulate host immunity. Antibodies against RSV G are a known correlate of protection. Previously, several broadly reactive, high-affinity anti-RSV G human monoclonal antibodies were isolated from RSV-exposed individuals and were shown to be protective in vitro and in vivo. Here, we determined the structures of three of these antibodies in complex with RSV G and defined distinct conformational epitopes comprised of highly conserved RSV G residues. Binding competition and structural studies demonstrated that this highly conserved region displays two non-overlapping antigenic sites. Analyses of anti-RSV G antibody sequences reveal that antigenic site flexibility may promote the elicitation of diverse antibody germlines. Together, these findings provide a foundation for next-generation RSV prophylactics, and they expand concepts in vaccine design for the elicitation of germline lineage-diverse, broadly reactive, high-affinity antibodies.

Distinct seasonality and increased respiratory failure in RSV patients < 2 years of age after emergence of SARS-CoV-2: data from the multicentric, prospective PAPI study

Respiratory syncytial virus (RSV) is a leading cause for global infant morbidity and mortality. The COVID-19 pandemic caused significant shifts in seasonality of RSV, and changes in disease severity have been matter of intense discussion. Between September 2020 and February 2023, the multicentric, prospective PAPI study analyzed rates and phenotypes of hospitalized RSV patients aged ≤ 24 months across three German hospitals. Pseudonymized patient data were analyzed employing Mann-Whitney U and chi-square testing, or one-way ANOVA or Kruskal-Wallis testing when more than two groups were compared. Additionally, RSV cases from seasons 2017/2018-2020/2021 were retrospectively analyzed. After its absence in 2020/2021, RSV returned approximately 2 months earlier than usual in late 2021. Overall duration of the season and patient numbers were comparable to previous seasons, and no significant shifts in age and gender distributions occurred in our cohort. While duration of hospitalization did not differ between the periods before vs. after the emergence of SARS-CoV-2, a significantly higher rate of patients with hypoxemia and respiratory failure occurred after the onset of the pandemic (oxygen supplementation post vs. pre: 59.4% vs. 54.8%, p < 0.001, non-invasive ventilation post vs. pre: 12.4% vs. 7.2%; p < 0.001). No deaths occurred during the entire observational period.

CONCLUSION

We present comprehensive data on distinct seasonality and increased disease severity in children hospitalized with RSV bronchiolitis before and after the onset of the SARS-CoV-2 pandemic. Our data aids in understanding the impact of the pandemic on RSV disease in infants and provides valuable information on the impact of RSV on pediatric healthcare prior to broad introduction of novel prevention measures such as nirsevimab.

WHAT IS KNOWN

• Respiratory syncytial virus (RSV) is a leading cause of infant morbidity and mortality globally. • COVID-19 has led to significant shifts in RSV seasonality, and concerns about shifts in RSV severity.

WHAT IS NEW

• This study shows distinct seasonality and significant shifts in diseases severity amongst children with RSV associated hospitalization under the age of 2 yrs in the last years in Germany. • It reports significantly higher rates of RSV associated respiratory failures in children < 2 yrs. of age after emergence of the pandemic.

Effectiveness of nirsevimab in preventing RSV-hospitalisation among young children in Western Australia 2024

BACKGROUND

Respiratory Syncytial Virus (RSV) causes a significant burden of illness for children under 2 years of age. Nirsevimab, a long-acting monoclonal antibody, was registered for RSV prevention in Australia in 2023. In April 2024, Western Australia (WA) launched the country's first state-wide nirsevimab program for all infants and high-risk children entering their second RSV season. This study describes the effectiveness of nirsevimab against RSV hospitalisation over a single epidemic season.

METHODS

Between April and October 2024, children hospitalised with laboratory-confirmed RSV-associated acute respiratory infection (ARI) and test-negative controls were enrolled from three hospitals in WA. Demographic variables, medical risk factors, symptoms and outcomes were assessed. Nirsevimab effectiveness in preventing RSV-associated hospitalisation was estimated.

RESULTS

Over 7 months, 284 children eligible for nirsevimab were enrolled including 184 RSV positive cases and 100 controls. Coverage of nirsevimab in RSV cases was 22.8% and 60.0% in controls. The overall adjusted effectiveness of nirsevimab against RSV-associated ARI hospitalisation was 88.2% (95% CI: 73.5, 94.7). RSV infection occurred in 42 (22.8%) children who had received nirsevimab; there was no significant difference in RSV illness severity among those immunised and unimmunised.

CONCLUSION

Nirsevimab was highly effective at preventing RSV-associated ARI hospitalisation in young children in the southern hemisphere.

SUMMARY

This study is the first Australian study to provide nirsevimab effectiveness estimate against RSV hospitalisation over a single epidemic season. The adjusted estimate of nirsevimab effectiveness against RSV-associated ARI hospitalisation was 88.2%, similar to those reported from Northern Hemisphere countries.

Effectiveness of nirsevimab in reducing hospitalizations in emergency departments due to bronchiolitis among infants under 3 months: a retrospective study

Respiratory syncytial virus (RSV) is a leading cause of infant morbidity. France has implemented a national campaign using nirsevimab to prevent RSV-related infections in infants. This study assessed its effectiveness in preventing hospitalization due to bronchiolitis in emergency department (ED). This retrospective study was conducted among six pediatric EDs in the Greater Paris area, France, and included infants aged < 3 months with a clinical diagnosis of bronchiolitis during the 2023-2024 RSV epidemic season. The primary outcome was hospitalization after the ED visits. The association with nirsevimab immunization was assessed using a multiple logistic model adjusted for potential confounding factors, with missing data handled using random forest imputation. Secondary analyses examined the risk of admission to the pediatric intensive care unit (PICU), RSV positivity, and subgroup analyses of prematurity, neonates, and deprivation using the FDep index (area-based measure of social deprivation in France). Between October 2 and December 31, 2023, 739 infants were included in the study. A total of 531 (72%) patients had a documented nirsevimab immunization status, and 402 (54%) were hospitalized following a bronchiolitis diagnosis. Nirsevimab showed 53.5% adjusted effectiveness in reducing hospitalizations (95% CI 34.1-67.3). Sensitivity analyses of complete-case data and propensity score matching yielded similar results. Nirsevimab also resulted in 51.1% reduction in PICU admissions (95% CI 10.7-74.3) and 79.6% reduction in RSV positivity (95% CI 68.0-87.1). The protective effect of immunization was consistent for preterm infants, neonates, and deprived groups, though the results were not statistically significant in these smaller subgroups.

CONCLUSIONS

Immunization with nirsevimab reduced hospitalization following an ED visit for bronchiolitis among infants aged < 3 months.

WHAT IS KNOWN

• Nirsevimab reduces the risk of bronchiolitis-related hospitalizations in clinical trials. • Real-world data from the immunization campaign in France remain limited.

WHAT IS NEW

• Nirsevimab showed 53.5% (95% CI 34.1-67.3) adjusted effectiveness in reducing hospitalizations for all-cause bronchiolitis in infants aged < 3 months in emergency departments. • Analyses included social deprivation and highlighted potential disparities in immunization access.

Regulation of respiratory syncytial virus nucleoprotein oligomerization by phosphorylation

The negative-sense RNA genome of respiratory syncytial virus (RSV) is encapsidated by the viral nucleoprotein N, forming a left-handed helical nucleocapsid which serves as template for the viral polymerase. Specific oligomerization of N along the viral genome necessitates a switch of conformation of N, from the neosynthesized monomeric and RNA-free N protein, named N0, to N-RNA oligomers. Although the binding of the N-terminal part of RSV phosphoprotein P plays the role of chaperone to impair RNA binding to N, N0-P interaction alone is not sufficient to prevent N oligomerization. Here, we explored the potential role of post translational modifications that could participate in the stability of N0. Among the post translational modifications specifically identified on recombinant monomeric N, we validated the presence of a phosphorylation site on residue Y88 of N which modulates N oligomerization. Our results suggest that RSV N oligomerization depends on the regulation by post translational modifications.

Genotypic and phenotypic characterisation of respiratory syncytial virus after nirsevimab breakthrough infections: a large, multicentre, observational, real-world study

BACKGROUND

Nirsevimab, a long-acting monoclonal antibody, has been approved for the prevention of respiratory syncytial virus (RSV) infection in infants. In France, more than 210 000 single doses were administered in infants younger than 1 year during the 2023-24 season. In this context, the selection and spread of escape variants might be a concern. Here, we aimed to characterise RSV associated with breakthrough infection.

METHODS

We did a multicentre, national, observational study in France during the 2023-24 RSV season in RSV-infected infants (aged <1 year) who either received or did not receive a dose of nirsevimab before their first RSV season. We excluded infants with insufficient information about nirsevimab treatment or without parental consent. We used respiratory samples collected in each laboratory for full-length RSV RNA sequencing to analyse changes in the nirsevimab binding site Ø. We tested clinical RSV isolates for neutralisation by nirsevimab. We analysed F candidate substitutions by fusion-inhibition assay.

FINDINGS

Of the 695 RSV infected infants, we analysed 545 (78%) full-length RSV genome sequences: 260 (48%) from nirsevimab-treated breakthrough infections (236 [91%] RSV-A and 24 [9%] RSV-B) and 285 (52%) from untreated RSV-infected infants (236 [83%] RSV-A and 49 [17%] RSV-B). Analysis of RSV-A did not reveal any substitution in site Ø known to be associated with resistance to nirsevimab. Two (8%) of 24 RSV-B breakthrough infections had resistance-associated substitutions: F:N208D (dominant resistance-associated substitution) and a newly described F:I64M plus F:K65R combination (minority resistance-associated substitution), both of which induced high levels of resistance in the fusion-inhibition assay.

INTERPRETATION

This study is, to the best of our knowledge, the largest genotypic and phenotypic surveillance study of nirsevimab breakthrough infections to date. Nirsevimab breakthrough variants remain very rare despite the drug's widespread use. The detection of resistance-associated substitutions in the RSV-B F protein highlights the importance of active molecular surveillance.

FUNDING

ANRS Maladies Infectieuses Emergentes and the French Ministry of Health and Prevention.

Hospital admissions for acute respiratory tract infections among infants from Nunavut and the burden of respiratory syncytial virus: a 10-year retrospective cohort study

Background

Nunavut is a northern Canadian territory where a high proportion of infants are admitted to hospital with acute respiratory tract infection (ARI). Previous studies have been limited in regional and/or short duration of coverage. This study aimed to estimate the incidence rate, microbiology and outcomes of ARI hospitalizations in Nunavut infants.

Methods

We conducted a retrospective cohort study of infants aged <1 year from Nunavut hospitalized for ARI at two regional and four tertiary pediatric hospitals in Canada, January 1, 2010, to June 30, 2020. One regional hospital was located in Nunavut; others were located across Canada. Descriptive statistics and multivariable logistic regression were performed.

Findings

We identified 1189 ARI admissions, with an incidence rate of 133.9 per 1000 infants per year (95% confidence interval (CI): 126.8, 141.3). Of these admissions, 56.0% (n = 666) were to regional hospitals alone, 72.3% (n = 860) involved hospitalization outside of Nunavut, 15.6% (n = 185) were admitted into intensive care, and 9.2% (n = 109) underwent mechanical ventilation. Among 730 admissions with a pathogen identified, 45.8% had respiratory syncytial virus (RSV; n = 334), for a yearly incidence rate of 37.8 RSV-associated hospitalizations per 1000 infants (95% CI: 33.9, 42.1). Among RSV-associated hospitalizations, 41.1% (n = 138) were infants 0-2 months of age and 32.1% (n = 108) were >6 months. Compared with non-RSV admissions, infants with RSV had higher odds of admission into intensive care, oxygen therapy, CPAP/BiPAP respiratory support and length of hospital stay over a week.

Interpretation

Understanding the high burden of ARI among Nunavut infants can inform health policy and serve as a baseline for assessing the impact of any new interventions targeting infant ARIs.

Funding

Public Health Agency of Canada and Canadian Institutes of Health Research via the Canadian Immunization Research Network (CNF 151944).

RSV Prevention Strategies in Korean Children: A Review of Current Approaches and Emerging Options

Respiratory syncytial virus (RSV) poses a significant threat to infants and young children in Korea and globally. Current preventive measures, such as palivizumab, have limitations, necessitating the exploration of new strategies. Nirsevimab, a long-acting monoclonal antibody, has emerged as a promising option for protecting all infants from RSV. Clinical trials and real-world evidence support its effectiveness in reducing RSV-related hospitalizations. The economic burden of RSV infection in Korea underscores the need for cost-effective interventions. While several RSV vaccines are under development, none are currently available in Korea. Maternal immunization programs and vaccines for older infants offer potential avenues for expanding protection. This review highlights the evolving landscape of RSV prevention, with a shift towards nirsevimab and future vaccines. Further research is crucial to understand the long-term consequences of RSV infection and develop comprehensive prevention strategies tailored to the Korean population.

Lung life HRQoL measure: psychometric properties and initial data in presumptive TB

INTRODUCTION

Health-related quality of life (HRQoL) data in young children with respiratory illnesses, including TB, are limited in low- and middle-income countries (LMICs). This study assessed the psychometric properties of the LuLi-Q measures in South African children with presumptive TB, focusing on children aged 0-5 years.

METHODS

In a cross-sectional study within the UMOYA TB diagnostic study, HRQoL data were collected using the LuLi-Q-Tots (0-2 years) and LuLi-Q-Pres (3-5 years) measures. Analyses included descriptive statistics, item-total correlations, and Cronbach's alpha for reliability.

RESULTS

Among 160 children aged 0-5 years (50 aged 0-2 years, 110 aged 3-5 years), the LuLi-Q-Tots had minimal floor and ceiling effects (6.5%), effectively capturing HRQoL. The LuLi-Q-Pres showed substantial floor and ceiling effects (61%), but removing 29 items improved reliability (Cronbach's alpha: 0.96-0.97). Caregivers reported daily medication use (54%) and anxiety (72%) in the 0-2 group, while separation anxiety (65%) and jealousy (92%) were common in the 3-5 group.

CONCLUSION

This study establishes a foundation for reliable HRQoL measures for young children with presumptive TB, guiding future research and patient-centred care in LMICs.

Multiplex Polymerase Chain Reaction Versus Standard Bacterial Culture in Critically Ill Children With Suspected Pneumonia

BACKGROUND

Bacterial lower respiratory tract infection, particularly ventilator-associated pneumonia (VAP), is a significant cause of morbidity and mortality in children who require mechanical ventilation (MV). Microbiologic diagnosis has relied on bacterial culture, but reverse transcriptase polymerase chain reaction (RT-PCR) with bacterial targets is now available for clinical use. We compared the diagnostic performance of tracheal aspirate (TA) multiplex RT-PCR to culture in children requiring MV with suspected lower respiratory tract infection.

METHODS

This is a secondary analysis of a prospective cohort of children (30 days to 18 years) at a single center requiring MV via an endotracheal tube for >72 hours in whom daily research TAs were collected. TAs were collected within 24 hours of clinically obtained cultures and analyzed by RT-PCR using the Biofire FilmArray Pneumonia Panel and compared with clinical culture results.

RESULTS

We compared the results of culture to RT-PCR for 56 samples at intubation and 74 samples from patients with suspected VAP. RT-PCR demonstrated increased detection of on-panel bacteria compared with culture (intubation 73.2% vs. 55.3% P = 0.048, suspected VAP 68.9% vs. 58.1%, P = 0.17) and had an overall sensitivity of 93.9%, specificity of 43.2% and negative predictive value of 92.1% for detection of pathogenic organisms. Overall, 33.8% of samples were positive by both methods, and 29.2% were negative by both methods. Two samples were positive by both methods but detected different on-panel organisms between culture and RT-PCR.

CONCLUSIONS

RT-PCR demonstrates high sensitivity and negative predictive value for the detection of on-panel pathogens in respiratory samples from critically ill children requiring MV. RT-PCR use may alter antibiotic prescriptions in this population.

Photoinduced Cleavage of Respiratory Syncytial Virus by Chiral Vanadium Trioxide Nanoparticles

Respiratory syncytial virus (RSV) poses a significant threat to the health of infants, children, and the elderly, and as of now there is a lack of effective therapeutic drugs. To tackle this challenge, chiral vanadium trioxide nanoparticles (V2O3 NPs) with a particle size of 2.56 ± 0.34 nm are successfully synthesized, exhibiting a g-factor value of 0.048 at 874 nm in terms of circular dichroism. Under 808 nm light irradiation, these chiral V2O3 NPs demonstrated selective cleavage of the RSV pre-fusion protein (RSV protein), effectively blocking its conformational rearrangement and preventing RSV infection both in vitro and in vivo. Experimental analysis revealed that the chiral V2O3 NPs specifically bind to the functional domain spanning from aspartate200 (D200) to asparagine208 (N208) in the primary sequence of the RSV protein. Notably, L-V2O3 NPs exhibited a higher affinity, which is 4.06 times that of D-V2O3 NPs and 13.55 times that of DL-V2O3 NPs. The precise cutting site is located between amino acid residues leucine204 (L204) and proline205 (P205), attributed to the reactive oxygen species (ROS) generated by photoinduced nanoparticles. In addition, L-V2O3 NPs inhibited RSV infection by 99.6% in nasal epithelial cells and 99.2% in Vero cells. In the RSV-infected mouse model, intranasal administration of L-V₂O₃ NPs effectively controlled the viral load in the lungs of mice, reducing it by 92.43%. The hematoxylin and eosin staining of mouse organs and serum biochemical indicators are similar to those of the wild-type group, indicating the biosafety of L-V₂O₃ NPs. The findings suggest that chiral nanoparticles hold great potential in controlling RSV and provide new directions and ideas for drug development against viruses.

Human respiratory syncytial virus genetic diversity and lineage replacement in Ireland pre- and post-COVID-19 pandemic

Human respiratory syncytial virus (HRSV) is a common cause of lower respiratory tract infections globally, and changes in viral epidemiology have been observed in many jurisdictions following the coronavirus disease 2019 (COVID-19) pandemic. Newly licensed vaccines and monoclonal antibodies are anticipated to alleviate the burden on healthcare systems, though such interventions may exert selective pressures on viral evolution. To evaluate the diversity of HRSV in Ireland pre- and post-COVID-19 pandemic, whole-genome sequencing was performed on HRSV-A (n=123) and -B (n=110) samples collected from community and hospitalized cases, during three HRSV seasons between 2021 and 2024. Additionally, G gene sequences, from HRSV-A (n=141) and -B (n=141), collected in the 2015-2019 period were examined. Lineages were assigned by phylogenetic analyses including reference lineages. Phylogenetic trees inferred with the G gene and whole genomes were consistent. Changes in the prevalence of certain lineages post-COVID-19 reflected the impact of non-pharmaceutical interventions (NPIs) introduced to reduce severe acute respiratory syndrome coronavirus 2 transmission, with A.D.1 and A.D.5 the dominant HRSV-A lineages and B.D.E.1 the most prevalent HRSV-B lineage. Similar trends were observed in HRSV lineages circulating across Europe during this time. The emergence of a new lineage was identified as a descendant from A.D.1, with eight distinctive substitutions in proteins G, F and L. Other circulating lineages with aa substitutions were observed in the F glycoprotein, which could impact nirsevimab binding. We provide the first comprehensive analysis of HRSV genomic diversity and evolution in Ireland over the last decade and the impact of the NPIs introduced during the COVID-19 pandemic. This study provides a foundation for future public health surveillance employing pathogen genomics to enable an evidence-based assessment of the impact of pharmaceutical interventions on HRSV evolution and disease severity.

Multiple Respiratory Virus Detection in Acute Respiratory Infection Patients in Mie Prefecture, Japan, 2021-2023

The Coronavirus disease 2019 (COVID-19) pandemic significantly impacted the circulation patterns of respiratory viruses worldwide. To better understand viral circulation patterns during the transition from pandemic to endemic phase, we conducted comprehensive respiratory virus surveillance in Mie Prefecture, Japan, during 2021-2023, coinciding with the Delta-to-Omicron transition of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). We collected respiratory specimens from acute respiratory infection patients in medical institutions, detecting 19 respiratory viruses using real-time PCR in 1573 valid samples out of 1605 specimens. Demographic and clinical data were available for some specimens. SARS-CoV-2 Omicron strains showed a peak positivity of 15-25% during the epidemic, while respiratory syncytial virus and human rhinovirus/enterovirus exhibited one to two annual epidemic peaks up to 57%, and human adenovirus maintained a positivity rate of 5-20% throughout the year. Age-dependent analysis revealed the significant detection of multiple viruses, particularly in children under 2 years, with up to six viruses detected simultaneously in those under 5 years. Our findings demonstrate varied respiratory virus prevalence patterns, with some viruses remaining active during the Omicron epidemic, suggesting its limited impact on other viruses. This comprehensive approach should enhance the understanding of respiratory virus epidemic dynamics and inform public health strategies.

Mucosal immunity elicited by a human-Fcγ receptor-I targeted intranasal vaccine platform enhances resistance against nasopharyngeal colonization of Streptococcus pneumoniae and induces broadly protective immunity against respiratory pathogens

The development of safe and effective mucosal vaccines are hampered by safety concerns associated with adjuvants or live attenuated microbes. We previously demonstrated that targeting antigens to the human-Fc-gamma-receptor-I (hFcγRI) eliminates the need for adjuvants, thereby mitigating safety concerns associated with the mucosal delivery of adjuvant formulated vaccines. Here we evaluated the role of the route of immunization in the mucosal immunity elicited by the hFcγRI-targeted vaccine approach. To enable Ag targeting, PspA from Streptococcus pneumoniae (Sp) was genetically fused with the hFcγRI-targeting antibody (α-hFcγRI) to generate PspA-FP. Intranasal (IN) immunization with the PspA-FP induced significantly higher IgA, IgG, and memory T cell response in the lung mucosa compared to that of the intramuscular (IM) route, while both routes exhibited similar increase in the systemic IgG response. The IN immunization elicited better resistance against nasal colonization (NC) of Sp compared to the IM immunization. Additionally, the resistance to NC with the IN administered PspA-FP was higher than the PspA-Alum formulation administered by the IM route. While the protection form lethal pulmonary Sp infection correlated with the systemic Ab response, the resistance from NC (of Sp) correlated with the mucosal immune response. Similar to the pneumococcal pneumoniae model, the hFcγRI-targeted vaccine (based on HA as Ag) was equally protective against pulmonary Influenza virus infection via both routes. However, the IN route promoted better protection compared to the IM route against a lethal pulmonary infection with Francisella tularensis (Ft). The enhanced protection against Ft correlated with the superior mucosal immune response elicited by the IN route compared to the IM route. These observations showed a differential requirement for mucosal delivery for protection depending on the type of pathogen. Moreover, this study revealed that the hFcγRI-targeted vaccine platform is broadly-effective as an adjuvant-free mucosal vaccine platform against respiratory pathogens.

Pregnant women's choices for preventing respiratory syncytial virus (RSV)

INTRODUCTION

Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis and pneumonia in infants and can lead to severe respiratory distress, especially in very young infants. No specific treatments exist for RSV. However, new preventative strategies have become available including RSV vaccine for pregnant women and monoclonal antibody for infants. This study aimed to identify and understand barriers and facilitators to the uptake of a new RSV vaccine in pregnant women and determine their underlying choices for a maternal RSV immunisation program. Additionally, the study investigated choice for maternal vaccination or administration of a long-lasting monoclonal antibody to infants.

METHODS

Eligible participants were pregnant women residing in Australia and aged 18 years or older. Focus group discussions and individual online interviews were conducted and data were analysed using a thematic analysis approach.

RESULTS

A total of 34 pregnant women participated in online focus group discussions or interviews, with an average age of 34 years. The identified themes were categorised into four overarching domains: 1) motivators for vaccinating during pregnancy to safeguard their babies and prevent severe diseases, 2) barriers to vaccination including vaccine safety concerns, uncertainties regarding vaccine effectiveness, and vaccine hesitancy arising from COVID-19 vaccination experiences, 3) preferred vaccination promotion strategies, including constant reminders/prompts, personalised messages, campaign focusing on serious outcomes and using diverse/lay languages, recommendations from local obstetricians and health authorities, 4) clear vaccine recommendation policies and a preference for maternal immunisation over infant immunisation.

CONCLUSIONS

The maternal RSV vaccination was generally welcomed and preferred by pregnant women in our study comparing to other strategies. Preferences for RSV program promotion included diversity in languages, "nudge" reminders, and recommendations from healthcare providers.

The role of viral interference in shaping RSV epidemics following the 2009 H1N1 influenza pandemic

Background

Disruptions in respiratory syncytial virus (RSV) activity were observed in different countries following the 2009 influenza pandemic. Given the limited use of non-pharmaceutical interventions, these disruptions do provide an opportunity to probe viral interference due to the out-of-season epidemics. The objectives of the study are twofold: to characterize atypical RSV activity in the United States (US) and to explore the mechanisms underlying changes in RSV epidemics following the pandemic.

Methods

Laboratory-confirmed RSV cases across 10 US regions from June 2007 to July 2019 were analyzed. A dynamic time warping method was used to characterize RSV activity in different seasons. A two-pathogen model was constructed to explore viral interference mechanisms. A sampling-importance resampling method was applied to estimate the effects of viral interference.

Results

We found that RSV activity was reduced following the influenza pandemic in the 2009/10 season across all regions in the US. By contrast, we found an enhanced but delayed RSV epidemic across the US in the 2010/11 season. Using a mathematical model, we identified three potential viral interference mechanisms that could explain the change of RSV activity following the pandemic. The pandemic influenza may interfere with RSV to reduce susceptibility to RSV coinfection, or shorten the RSV infectious period, or decrease RSV infectivity in co-infections.

Conclusions

This study provides statistical evidence for atypical RSV seasons following the influenza pandemic in the US and sheds light on viral interference mechanisms affecting RSV epidemics, offering a model-fitting framework for analyzing surveillance data at the population level.

Epidemiological Changes in Hospitalized Bronchiolitis in Children Under 2 Years of Age in Hangzhou Before and After COVID-19 Restriction Easing

Background

Bronchiolitis is a common cause of hospitalization in infants under 2 years of age. The epidemiological effects of changes in hygiene and social behaviors during COVID-19 restrictions on the disease is still debated. This study aimed to analyze the changes in the viral etiology of bronchiolitis in Hangzhou during the COVID-19 restriction period (2022) compared to the period following the easing of restrictions(2023).

Methods

This study collected data on patients under 2 years of age who were admitted for bronchiolitis to the Department of Pulmonology at the Children's Hospital, Zhejiang University School of Medicine (Hangzhou) from January, 1, 2022, to December 31, 2023. It also investigated seasonal variations in the incidence of bronchiolitis and pathogen distribution across different years.

Results

This study included a total of 697 children with bronchiolitis, with a median age of 7.5 (4.2-12.0) months. Of these, 68.9% were boys and 31.1% were girls. Compared to 2022, the number of bronchiolitis cases in 2023 (388 versus 309) and their proportion of lower respiratory tract infections (39.1% versus 28.2%) have significantly increased (p < 0.001). Whether in 2022 or 2023, respiratory syncytial virus (RSV) was the primary pathogen causing bronchiolitis among children under 12 months of age, while human rhinovirus (HRV) was the main pathogen in children aged 12-24 months. There was a shift in the timing of the peak of several viruses including RSV, human metapneumovirus (HMPV) and parainfluenza virus (PIV) infections in 2023. However, the epidemic trend of HRV presented no significant changes between 2022 and 2023.

Conclusion

The findings suggest that bronchiolitis hospitalizations increased markedly after COVID-19 restriction easing, particularly among children aged 12-18 months. There was a shift in the timing of the peak of several viruses including RSV, HMPV and PIV infections in 2023, emphasizing the need for hospitals to anticipate potential irregularities in time in the future.

Adherence to Palivizumab for Respiratory Syncytial Virus Prophylaxis in Romanian Infants

BACKGROUND

In 2022, Romania started an RSV immunoprophylaxis program with Palivizumab for infants at high risk: preterm infants born before 35 weeks of pregnancy, infants born with congenital heart defects, and infants with chronic lung disease. We evaluated treatment adherence from August 2022 to March 2024.

METHOD

We monitored the increase in the number of patients enrolled in the program and the number of collaborating neonatologists, family doctors, and pediatricians. Adherence to all doses of Palivizumab in enrolled patients was assessed by telephone interviews. The factors contributing to reduced adherence were identified.

RESULTS

Between August 2022 and March 2024, 1903 patients and 233 specialists were enrolled, a steady increase in both cohorts. The percentage of patients that complete their full sequence of doses decreases along with the number of doses (99% for one dose, 73% for two doses, 47% for three doses, 35% for four doses, and 22% for five doses) due to several factors.

CONCLUSIONS

The program remains highly regarded by both physicians and caregivers, demonstrating its effectiveness as a valuable resource for educating parents and facilitating monoclonal antibody administration as a prevention method for RSV.

Hospitalizations for bronchiolitis among infants before and after the SARS-CoV-2 pandemic: an area-based study of the Emilia-Romagna Region, Italy

BACKGROUND

Bronchiolitis is the most frequent lower respiratory tract infection and a leading cause of hospitalization in infants. Our aim was to assess the incidence and characteristics of bronchiolitis requiring hospital admission in an Italian region before and after the SARS-CoV-2 pandemic.

METHODS

This area-based retrospective study analyses 4,396 hospital discharge records (HDR) of children under 1 year of age admitted with a diagnosis of bronchiolitis (ICD9-CM codes 466.11 and 466.19), in Emilia-Romagna (Italy) from January1st, 2018 to December 31th, 2021. Weighted t-testing and Z-testing was carried out.

RESULTS

in the study period, 2-4% of infants were admitted for bronchiolitis (10% of all admissions under 1 year) and 59% of them were aged less than 90 days. After a significant decrease in 2020, bronchiolitis resurged in 2021, and Respiratory Syncytial Virus (RSV) cases reached 82%. RSV cases were more likely to undergo non-invasive ventilation (NIV), oxygen supplementation and to receive i.v. (intravenous) infusions. There was an overall increasing trend in NIV and oxygen supplementation, and a decreasing trend in chest X-rays.

CONCLUSIONS

This area-based study shows reduced hospital admissions due to bronchiolitis during the SARS-CoV-2 pandemic and a resurgence of RSV infection after the easing of preventive measures. We also provide information on length of stay and need for hospital treatments. These area-based information will be helpful in assessing the impact of future universal prevention measures.

Estimating the cost-effectiveness of maternal respiratory syncytial virus (RSV) vaccination in Australia: A dynamic and economic modelling analysis

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of respiratory illness, with younger infants at greatest risk of hospitalisation. With the recent approval of a maternal RSV vaccine in Australia, it is timely to evaluate its potential costs and health benefits in Australia.

METHODS

We applied an integrated dynamic and economic evaluation model to estimate specific outcomes of RSV disease and the cost-effectiveness of a year-round maternal RSV vaccination program in Australia. Cost-effectiveness was estimated using the incremental cost-effectiveness ratio (ICER) per quality-adjusted life year (QALY) gained.

RESULTS

From a healthcare system perspective, the maternal vaccination program was estimated to be cost-effective at a vaccine price less than approximately 120 Australian dollars ($AU), assuming a willingness-to-pay (WTP) threshold of $AU 50,000/QALY gained. Most of the estimated cost-savings were from preventing RSV hospitalisations in infants aged <6 months. However, while 82% of the cost-savings were from preventing RSV hospitalisations in infants aged <6 months, only about 25% of the QALY gains were in this age group. The majority of the other QALY gains came via herd effects from prevention of death in older adults and to a lesser extent, prevention of nonmedically-attended illness in older teens and adults. When predicted cost-savings and QALY gains in those ≥6 months of age were excluded, the vaccine price required to meet the assumed WTP threshold fell to $AU 63.

CONCLUSIONS

A maternal RSV vaccination program in Australia could provide value for money by reducing hospitalisations and associated costs among infants aged <6 months, depending on the vaccine price. We have provided evidence that herd effects beyond the target population may be an important consideration in assessing cost-effectiveness of maternal RSV vaccination.

Respiratory Syncytial Virus Vaccine and Nirsevimab Uptake Among Pregnant People and Their Neonates

Importance

Two interventions to prevent severe respiratory syncytial virus (RSV) in infants were approved in 2023-a bivalent prenatal RSV prefusion F protein-based (RSVpreF) vaccine and an infant monoclonal antibody (nirsevimab). Understanding their uptake and clinical outcomes is essential for public health planning.

Objective

To describe uptake of the prenatal RSVpreF vaccine and infant nirsevimab.

Design, Setting, and Participants

This retrospective cohort study was conducted at a single academic center among 647 pregnant individuals eligible for RSVpreF vaccination (32-36 weeks' gestation between October 15, 2023, and January 31, 2024) and infants eligible for nirsevimab (no prenatal RSVpreF vaccination >14 days before delivery).

Exposure

Pregnancy or birth during the 2023-2024 RSV season.

Main Outcomes and Measures

RSVpreF vaccination among eligible pregnant individuals and nirsevimab administration prior to hospital discharge among eligible infants.

Results

Of 647 eligible pregnant individuals (mean [SD] age, 34.6 [6.2] years; 355 nulliparous [54.9%]; 558 privately insured [86.2%]), 414 (64.0%) received the RSVpreF vaccine. Factors associated with higher RSVpreF uptake included older birthing parent age (adjusted odds ratio [AOR], 1.09; 95% CI, 1.05-1.12), nulliparity (AOR, 1.84; 95% CI, 1.31-2.60), private insurance (AOR, 2.19; 95% CI, 1.27-3.80), non-Hispanic ethnicity (AOR, 2.36; 95% CI 1.57-3.55; reference: Hispanic), receipt of any COVID-19 vaccine (AOR, 7.12; 95% CI, 3.91-13.70), 2023-2024 formula COVID-19 booster vaccine (AOR, 5.62; 95% CI, 3.80-8.48), influenza vaccine (AOR, 8.14; 95% CI, 5.38-12.50), or tetanus-diphtheria-pertussis vaccine (AOR, 6.86; 95% CI, 3.79-13.10). Factors associated with lower RSVpreF uptake included non-English language preference (AOR, 0.24; 95% CI, 0.10-0.52), Black race (AOR, 0.30; 95% CI, 0.16-0.57; reference: Asian), other or unknown race (AOR, 0.48; 95% CI, 0.30-0.76), and multiple gestation (AOR, 0.27; 95% CI, 0.07-0.88). Nirsevimab was administered to 183 of 261 eligible infants (70.1%) prior to hospital discharge. Among those who did not receive RSVpreF or standard prenatal vaccines, 40.4% of their neonates (19 of 47) received nirsevimab; among those who declined infant hepatitis B vaccination, 34.0% of their neonates (17 of 50) received nirsevimab. Respiratory syncytial virus coverage exceeded 80% during all months of the study period except October 2023, the first month during which prenatal RSV vaccination and infant nirsevimab were available. Preterm delivery occurred in 35 of 414 RSVpreF-vaccinated individuals (8.5%) and 43 of 233 unvaccinated individuals (18.5%). In a nested case-control analysis with preterm birth as the outcome, there was no significant association between RSVpreF vaccination and preterm birth (AOR, 1.03; 95% CI, 0.55-1.93).

Conclusions and Relevance

In this cohort study, uptake of the RSVpreF vaccine and infant nirsevimab was high. Nirsevimab uptake was high even among individuals who did not receive routine prenatal or infant vaccines. There was no significant association between RSVpreF vaccination and preterm birth. This study suggests that an RSV prevention strategy that included both prenatal vaccination and infant monoclonal antibody administration had high uptake and reassuring perinatal outcomes.

Incidence of and Risk Factors for Subsequent Lower Respiratory Tract Infection Following an Infant RSV Hospitalization

Background/Objectives: Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and pneumonia in infants and the leading cause of infant hospitalization in the U.S. and worldwide. The risk of experiencing at least one other medically attended lower respiratory tract infection (MA LRTI) following an infant RSV hospitalization is less studied. Methods: We conducted a retrospective cohort study of infants who experienced an RSV hospitalization (index hospitalization) during infancy. The incidence rate of having a subsequent MA LRTI was reported. The association between a priori selected maternal and infant risk factors and subsequent MA LRTI was determined. Results: Of the 20,181 children who experienced an RSV hospitalization in infancy, 15% had at least one subsequent MA LRTI within the same RSV season. The incidence rates (95% confidence interval) of having a subsequent MA LRTI hospitalization, emergency department visit, or physician office visit in the same RSV season were 0.27 (0.26, 0.29), 0.16 (0.15, 0.17), and 0.46 (0.44, 0.48) per infant-year, respectively. Factors associated with an increased risk of subsequent MA-LRTI include younger maternal age, fewer years of maternal education, smoking during pregnancy, cesarean delivery, male infant sex, White race, siblings at home, urban residence, lower birth weight, lower gestational age, eligibility for and/or ever receiving palivizumab, longer birth hospitalization length of stay, longer index RSV hospitalization length of stay, intensive care unit admission for the index hospitalization, and summer-to-fall births. Conclusions: The burden of clinically significant subsequent MA-LRTI following an RSV hospitalization can be substantial. Our results highlight the importance of increasing accessible RSV LRTI preventive interventions.

Effectiveness of catch-up and at-birth nirsevimab immunisation against RSV hospital admission in the first year of life: a population-based case-control study, Spain, 2023/24 season

BackgroundRespiratory syncytial virus (RSV) causes substantial morbidity in infants < 1 year. In October 2023, Spain recommended the monoclonal antibody nirsevimab to all children born since 1 April 2023, at birth or as catch-up if born before October 2023.AimWe estimated nirsevimab effectiveness in preventing RSV hospitalisations during the 2023/24 season.MethodsWe conducted a nationwide population-based matched case-control study. Cases were children hospitalised for lower respiratory tract infection who were RSV PCR-positive. For each case, we selected four population density controls born in the same province and date (±2 days). We defined at-birth immunisation as receiving nirsevimab during the first 2 weeks of life, and catch-up immunisation within 30 days from campaign onset. Causal intention-to-treat (ITT) and per-protocol (PP) effectiveness was estimated using inverse-probability-of-immunisation weighted conditional logistic regression.ResultsWe included 406 cases and 1,623 controls in catch-up and 546 cases and 2,182 controls in at-birth immunisation studies. Effectiveness in preventing RSV hospitalisations for catch-up immunisation was 71% (95% confidence interval (CI): 65-76) by ITT and 80% (95% CI: 75-84) PP. Effectiveness for at-birth immunisation was 78% (95% CI: 73-82) by ITT and 83% (95% CI: 79-87) PP. Effectiveness was similar for ICU admission, need of mechanical ventilation, and RSV viral subgroups A and B. Children born pre-term or with birthweight < 2,500 g showed lower PP effectiveness of 60-70%.ConclusionsPopulation-level nirsevimab immunoprophylaxis in children in their first RSV season was very effective in preventing RSV hospitalisations, ICU admission and mechanical ventilation, with reduced but still high effectiveness for pre-term and low-birthweight children.

Knowledge About Respiratory Syncytial Virus and Acceptance of Infant Monoclonal Antibody for RSV and RSV Vaccination During Pregnancy

BACKGROUND

Respiratory syncytial virus (RSV) is the leading cause of hospitalization among infants in the United States (US). RSV immunization, in the form of a monoclonal antibody (mAb) for infants and vaccines for pregnant people, may reduce infant RSV risk.

METHODS

In April and May 2023, we surveyed adults with children in Oregon and Washington about the likelihood to accept infant mAb and maternal RSV vaccine and RSV awareness. We used multivariable logistic regression to identify predictors of self-reported likelihood of accepting RSV immunization.

RESULTS

Among 1082 respondents, 68% and 70% responded they would very likely accept infant mAb or maternal RSV vaccine, respectively. Respondents had lower odds of accepting infant mAb (OR: 0.10, 95% CI: 0.07-0.15) and maternal RSV vaccine (OR: 0.16, 95% CI: 0.12-0.23) if they were somewhat or very concerned about side effects. Respondents had higher odds of accepting infant mAb if they received an influenza vaccination (OR: 3.79, 95% CI: 1.88-7.63). Respondents had higher odds of accepting maternal vaccine if they had an advanced degree (OR: 1.70, 95% CI: 1.06-2.73), had received an influenza vaccination (OR: 3.62, 95% CI: 1.80-7.25), or were aware of RSV before our survey (OR: 2.03, 95% CI: 1.03-4.01).

CONCLUSION

Most respondents reported that they would likely accept RSV mAb for their infant or an RSV vaccine during pregnancy. Concerns about side effects lowered the odds of accepting immunization, however, nearly one-half of those concerned about side effects still expressed a high likelihood of accepting either immunization.

Harnessing Epigenetics: Innovative Approaches in Diagnosing and Combating Viral Acute Respiratory Infections

Acute respiratory infections (ARIs) caused by viruses such as SARS-CoV-2, influenza viruses, and respiratory syncytial virus (RSV), pose significant global health challenges, particularly for the elderly and immunocompromised individuals. Substantial evidence indicates that acute viral infections can manipulate the host's epigenome through mechanisms like DNA methylation and histone modifications as part of the immune response. These epigenetic alterations can persist beyond the acute phase, influencing long-term immunity and susceptibility to subsequent infections. Post-infection modulation of the host epigenome may help distinguish infected from uninfected individuals and predict disease severity. Understanding these interactions is crucial for developing effective treatments and preventive strategies for viral ARIs. This review highlights the critical role of epigenetic modifications following viral ARIs in regulating the host's innate immune defense mechanisms. We discuss the implications of these modifications for diagnosing, preventing, and treating viral infections, contributing to the advancement of precision medicine. Recent studies have identified specific epigenetic changes, such as hypermethylation of interferon-stimulated genes in severe COVID-19 cases, which could serve as biomarkers for early detection and disease progression. Additionally, epigenetic therapies, including inhibitors of DNA methyltransferases and histone deacetylases, show promise in modulating the immune response and improving patient outcomes. Overall, this review provides valuable insights into the epigenetic landscape of viral ARIs, extending beyond traditional genetic perspectives. These insights are essential for advancing diagnostic techniques and developing innovative treatments to address the growing threat of emerging viruses causing ARIs globally.

Respiratory Syncytial Virus Epidemiology in Argentina: From COVID-19 Pandemic to the Maternal Immunization Strategy

INTRODUCTION

Worldwide, respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections (LRTIs) and hospital admissions among infants and young children. The COVID-19 pandemic changed the epidemiology and clinical patterns of respiratory viruses other than severe acute respiratory syndrome coronavirus 2. Argentina introduced the RSV maternal vaccine in 2024. This multicenter study describes the clinical-epidemiological profile of hospitalized pediatric patients with LRTI associated with RSV in Argentina, comparing pre- and postpandemic periods, and identifies independent predictors of RSV infection.

MATERIALS AND METHODS

This prospective, multicenter study included patients under 18 years old admitted for LRTI in 5 tertiary centers in Argentina before (2018-2019) and after (2022-2023) COVID-19. Changes in viral detection rates, seasonality, epidemiological and clinical characteristics were analyzed. Indirect immunoassay or real-time polymerase chain reaction were used for virological diagnosis prepandemic and real-time polymerase chain reaction for postpandemic. Data analysis was performed using Epi Info 7.

RESULTS

A total of 5838 LRTI cases were included (mean age: 9.5 months; interquartile range: 4-22 months), with 96.6% tested for viral detection, and 66.4% positive (3877 cases). RSV was the most prevalent virus, followed by parainfluenza and influenza. Postpandemic, there was a significant decrease in RSV prevalence and an increase in parainfluenza and metapneumovirus infections. LRTI seasonality shifted 6 weeks forward postpandemic. In 2022, metapneumovirus cases increased, displacing RSV, which recovered prevalence and typical seasonality in 2023 with an earlier onset. Viral coinfection occurred in 17.2% of RSV cases. Globally, 71% of RSV cases were infants under 12 months (45.8%, <6 months); bronchiolitis was the most common clinical presentation (68.9%), with cough (78.3%), respiratory distress (69.6%), rhinorrhea (65.9%) and fever (64.7%) being the most common symptoms. Nearly 44% had underlying conditions, 15.7% were born preterm, 15% required intensive care and 24% received empirical antibiotics. The pre- and postpandemic periods showed no age differences in RSV-associated LRTI cases, but higher comorbidity prevalence, intensive care requirement and lower empirical antibiotic use postpandemic. Prematurity [odds ratio (OR): 1.3, 95% confidence interval (CI): 1.1-1.5; P = 0.004], comorbidities (OR: 1.8, 95% CI: 1.6-2; P < 0.001) and age under 6 months (OR: 1.8, 95% CI: 1.6-2.1; P < 0.001) were independent predictors of RSV infection.

CONCLUSIONS

RSV primarily affected infants under 1 year old. No age differences were found between LRTI cases associated with RSV pre- and postpandemic. Postpandemic, there was a higher prevalence of comorbidities, increased intensive care requirements and lower empirical antibiotic use. Prematurity, underlying conditions and age under 6 months were independent predictors of RSV infection in hospitalized LRTI patients.

Nirsevimab effectiveness on paediatric emergency visits for RSV bronchiolitis: a test-negative design study

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%). Among case patients, 27/274 (9.8%) received nirsevimab, compared to 50/109 (46.2%) among control patients. Nirsevimab had an adjusted estimated effectiveness of 82.5% (95% CI [68.0-90.8]) at PEDs. Sensitivity analyses found similar results. At 15-day follow-up, characteristics were similar between children immunized by nirsevimab or not.

CONCLUSION

Our findings advocate for nirsevimab widespread adoption to alleviate the burden of RSV bronchiolitis in paediatric emergency departments.

TRIAL REGISTRATION

NCT04743609 (date of registration: February 4, 2021).

WHAT IS KNOWN

• Each year, RSV-bronchiolitis places significant pressure on pediatric emergency services. • France is one of the first countries in the world to have implemented nirsevimab in septembre 2023.

WHAT IS NEW

• Nirsevimab effectiveness on pediatric emergency visits for RSV-bronchiolitis has been estimated to 82.5% (95% CI [68.0-90.8]) in our study. • The effectiveness was as strong to prevent hospitalizations and sever illnesses.

Economic Impact of Respiratory Syncytial Virus Infections in Children Under 5 Years of Age Attending Primary Care in Italy: A Prospective Cohort Study in Two Regions

BACKGROUND

Accurate cost estimates of respiratory syncytial virus (RSV) infections in primary care are limited, despite the majority of cases being managed in this setting. This study aims to estimate healthcare costs for children with RSV in primary care and the related costs of parental work absence.

METHODS

Children < 5 years of age with symptoms of acute respiratory infections were recruited via primary care paediatricians in two Italian regions for a prospective cohort study on the RSV burden in primary care, during the 2019/2020 winter. Healthcare utilization, medication use and parental work absence were assessed during a 14-day follow-up period. Average costs were estimated per RSV episode for the overall study population, as well as per age group.

RESULTS

Two hundred ninety three children were recruited, of which 119 tested RSV positive (41%) and 109 were included. In total, 89% of RSV-positive children (97/109) had ≥ 1 repeat paediatrician visit(s), and 10% (11/109) visited the ED. The mean number of repeat visits was 3.8 (SD: 4.0) and the mean duration of work absence 4.0 days (SD: 5.0). Average costs per RSV episode were €730 (95% CI: €691-€771), with direct medical costs accounting for 25% (€183 [95% CI: €174-€191]) and indirect costs related to work absence for 75% (€547 [95% CI: €509-€587]).

CONCLUSIONS

Costs associated with RSV infections in young children in primary care are considerable due to a substantial number of paediatrician visits and high rates of parental work absence. These costs are important to include in decision-making regarding the implementation of new RSV immunization strategies in national immunization programmes.

Impact of RSVpreF vaccination on reducing the burden of respiratory syncytial virus in infants and older adults

Respiratory syncytial virus (RSV) causes a substantial health burden among infants and older adults. Prefusion F protein-based vaccines have shown high efficacy against RSV disease in clinical trials, offering promise for mitigating this burden through maternal and older adult immunization. Employing an individual-based model, we evaluated the impact of RSV vaccination on hospitalizations and deaths in 13 high-income countries, assuming that the vaccine does not prevent infection or transmission. Using country-specific vaccine uptake rates for seasonal influenza, we found that vaccination of older adults would prevent hospitalizations by a median of 35-64% across the countries studied here. Vaccination of pregnant women could avert infant hospitalizations by 5-50%. Reductions in RSV-related mortality mirrored those estimated for hospitalizations. While substantial hospitalization costs could be averted, the impact of vaccination depends critically on uptake rates. Enhancing uptake and accessibility is crucial for maximizing the real-world impact of vaccination on reducing RSV burden among vulnerable populations.

Current antiviral therapies and promising drug candidates against respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is one of the most common viruses leading to lower respiratory tract infections (LRTIs) in children and elderly individuals worldwide. Although significant progress in the prevention and treatment of RSV infection was made in 2023, with two anti-RSV vaccines and one monoclonal antibody approved by the FDA, there is still a lack of postinfection therapeutic drugs in clinical practice, especially for the pediatric population. In recent years, with an increasing understanding of the pathogenic mechanisms of RSV, drugs and drug candidates, have shown great potential for clinical application. In this review, we categorize and discuss promising anti-RSV drug candidates that have been in preclinical or clinical development over the last five years.

The link between respiratory syncytial virus (RSV) morphogenesis and virus transmission: Towards a paradigm for understanding RSV transmission in the upper airway

Respiratory syncytial virus (RSV) particle assembly occurs on the surface of infected cells at specialized membrane domain called lipid rafts. The mature RSV particles assemble as filamentous projections called virus filaments, and these structures form on the surface of many permissive cell types indicating that this is a robust feature of the RSV particle assembly. The virus filaments also form on nasal airway organoids systems providing evidence that these structures also have a clinical relevance. Virus filaments also form on cells infected with the closely related human metapneumovirus, suggesting that virus filament formation may be a common feature of assembly process for viruses within the Pneumoviridae family. During RSV infection these virus filaments mediate the localized cell-to-cell spread of virus infection, suggesting that they play an important role in virus transmission. The current understanding of the connection between virus filament formation and virus transmission during RSV infection is presented.

Preventing RSV Infection in Children: Current Passive Immunizations and Vaccine Development

Human respiratory syncytial virus (RSV) is a leading cause of acute respiratory tract infection and lower respiratory tract infection, associated with high morbidity and mortality in young children, the elderly, and immunocompromised individuals. Initial attempts to develop an RSV vaccine in the 1960s were faced with a setback due to the enhanced RSV disease developed by vaccinated children. More recent advancements have led to the generation of RSV vaccines for older adults and pregnant women. However, there are still no commercially available RSV vaccines for infants. This work summarizes the current passive immunizations and the ongoing efforts to develop an RSV vaccine for infants.

Nationwide Epidemiology and Outpatient Healthcare Resource Use of Children with Respiratory Syncytial Virus from 2005 to 2021

BACKGROUND

Respiratory syncytial virus (RSV) poses a global health challenge, particularly among younger children. While the disease burden in Japan has been preliminarily quantified in short-term or inpatient settings, a comprehensive understanding of outpatient settings at a national level is still lacking.

METHODS

In this retrospective cohort study, we followed 697 802 children until they reached 60 months of age, amounting to 25 680 468 million person-months, using two nationally representative databases from the fiscal years 2005-2021. We analyzed trends in the epidemiology of RSV infections and associated outpatient health resource use.

RESULTS

Incidence rates of RSV and associated hospitalizations among infants showed fluctuations of 50-100 cases and 20-30 hospitalizations per 1000 person-years, respectively, during the 2010s. These rates dropped to 8.7 cases and 2.2 hospitalizations per 1000 person-years in 2020, then returned to the same levels in the 2010s. Similar patterns were noted for RSV testing, outpatient visits, healthcare cost, and the proportion of cases hospitalized (case-hospitalization risk). Whereas antibiotic use decreased from 56.4% in 2005 to 27.8% in 2021, palivizumab use increased from 95.2 to 195.9 days of therapy per 1000 person-years. Applying the calculated incidence rates to national data, annual outpatient healthcare costs for RSV infections were estimated to be 7-9 billion JPY (50-64 million USD) for children aged < 60 months in the late 2010s.

CONCLUSIONS

Our study highlights the changes in epidemiology and outpatient health resource utilization for children with RSV infections. These findings are valuable for policymakers and clinicians aiming to develop strategies, including newly developed maternal vaccines and single-dose long-acting monoclonal antibodies.

Infant RSV infection desensitizes β2-adrenergic receptor via CXCL11-CXCR7 signaling in airway smooth muscle

Rationale

Airflow obstruction refractory to β2 adrenergic receptor (β2AR) agonists is an important clinical feature of infant respiratory syncytial virus (RSV) bronchiolitis, with limited treatment options. This resistance is often linked to poor drug delivery and potential viral infection of airway smooth muscle cells (ASMCs). Whether RSV inflammation causes β2AR desensitization in infant ASMCs is unknown.

Objectives

To investigate the interaction of RSV inflammation with the β2AR signaling pathway in infant ASMCs.

Methods

Infant precision-cut lung slices (PCLSs) and mouse pup models of RSV infection were subjected to airway physiological assays. Virus-free, conditioned media from RSV-infected infant bronchial epithelial cells in air-liquid interface (ALI) culture and nasopharyngeal aspirates (NPA) from infants with severe RSV bronchiolitis were collected and applied to infant PCLSs and ASMCs. Cytokines in these samples were profiled and assessed for the effects on β2AR expression, cell surface distribution, and relaxant function in ASMCs.

Measurements and Main Results

Conditioned media and NPA induced similar resistance to β2AR agonists in ASMCs as RSV infection. Cytokine profiling identified CXCL11 as one of the most elevated signals following RSV infection. CXCL11 activated its receptor CXCR7 in a complex with β2AR in ASMCs to promote β2AR phosphorylation, internalization, and degradation. Blockade of CXCR7 partially restored airway relaxation in response to β2AR agonists in infant PCLSs and mouse pup models of RSV infection.

Conclusions

The CXCL11-CXCR7 pathway plays a critical role in β2AR desensitization in ASMCs during RSV infection and represents a potential therapeutic target in alleviating airflow obstruction in infant RSV bronchiolitis.

Infants display reduced NK cell responses in RSV and increased inflammatory responses in SARS-CoV-2 infections

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection hospitalizations in infants and poses a significantly higher risk of respiratory failure than SARS-CoV-2. The mechanisms underlying these differences remain unclear. We analyzed blood samples from infants (median age 2.3 months) with SARS-CoV-2 (n = 30), RSV (n = 19), and healthy controls (n = 17) using single-cell transcriptomics and epigenomics, and cytokine profiling. Both viruses triggered comparable interferon responses across PBMC subsets but differed in NK cell and inflammatory responses. Severe RSV cases showed reduced NK cell frequencies, lower IFNG expression, and decreased chromatin accessibility at T-BET and EOMES binding sites. RSV infections were also associated with increased CD4+ TEMRA, memory Treg and transitional B cells. In contrast, SARS-CoV-2 was characterized by stronger pro-inflammatory signatures, including increased NFKB pathway activity and higher serum TNF concentrations. These findings highlight distinct immune responses to RSV and SARS-CoV-2, providing insights that may inform clinical decisions.

Surfactant Protein-A and its immunomodulatory roles in infant respiratory syncytial virus infection: a potential for therapeutic intervention?

The vast majority of early-life hospital admissions globally highlight respiratory syncytial virus (RSV), the leading cause of neonatal lower respiratory tract infections, as the major culprit behind the poor neonatal outcomes following respiratory infections. Unlike those of older children and adults, the immune system of neonates looks rather unique, therefore mostly counting on the innate immune system and antibodies of maternal origins. The collaborations between cells and immune compartments during infancy inclines bias toward a T-helper 2 (Th2) immune profile and thereby away from a T-helper 1 (Th1) immune response. What makes it more problematic is that RSV infection also tends to elicit a stronger Th2-biased immune response and drive an aberrant allergy-like inflammation. It is thus evident how RSV infections potentially pave the way for wheezing recurrences and childhood asthma later in life. Surfactant, the essential lung substance for normal breathing processes in mammals, has immunomodulatory properties including lung collectins such as Surfactant Protein-A (SP-A), which is the most abundant protein component of surfactant, and also Surfactant Protein-D (SP-D). Deficiency of SP-A and SP-D has been found to be associated with impaired pathogen clearance and exacerbated immune responses during infections. We therefore conducted a review of the literature to describe pathomechanisms of RSV infections during blunted neonatal immunity potentially facilitating allergy-like inflammatory events within the developing lungs and highlight the potential protective role of the humoral collectin SP-A to mitigate these in the "early in life" pulmonary immune system.

Attitude to RSV Vaccination Among a Cohort of Pregnant Women in Jordan: A Cross-Sectional Survey Study

Background and Aims

The recently approved maternal vaccination against respiratory syncytial virus (RSV) can reduce its burden among infants. However, vaccine hesitancy/resistance can undermine the beneficial impact of RSV vaccination. The aim of this study was to assess the willingness of pregnant women in Jordan to receive RSV vaccination and its associated determinants.

Methods

Face-to-face interviews were conducted in obstetrics/gynecology clinics in the Central, Northern, and Southern regions of Jordan during January-February 2024, using a convenience sampling approach. Attitude to RSV vaccination was assessed using the previously validated ABCDEF scale.

Results

A total of 404 pregnant women participated in the study with a mean age of 30.1 ± 6.2 years. A majority of the participants showed willingness to receive RSV vaccination (n = 313, 77.5%), with hesitancy among 25 participants (6.2%), and resistance among 66 participants (16.3%). Variables that were significantly associated with a higher RSV vaccine acceptance in multivariate analysis were: age < 30 years (adjusted odds ratio (aOR): 2.45, p = 0.010), undergraduates (aOR: 3.27, p = 0.026), being a healthcare worker (aOR: 4.50, p = 0.036), and the history of previous COVID-19/influenza vaccine uptake (aOR: 2.47, p = 0.045). Two out of the six ABCDEF constructs were significantly associated with RSV vaccine acceptance, namely the "Advice" construct (aOR: 10.38, p < 0.001) and the "Fear" construct (aOR: 21.49, p < 0.001).

Conclusion

This study highlighted the complex nature of attitude towards maternal RSV vaccination among pregnant women. The study showed the role of demographic variables, prior vaccination experience, trust in credible health institutions and vaccine safety, and the fear of RSV disease consequences in infants in shaping maternal attitude to RSV vaccination. Addressing these factors can help to effectively promote RSV vaccine uptake among pregnant women, subsequently helping to protect infants from the significant RSV disease burden.