Burden of respiratory syncytial virus infection in community-dwelling older adults in Europe (RESCEU): an international prospective cohort study

Host immune response to respiratory syncytial virus infection and its contribution to protection and susceptibility in adults: a systematic literature review

INTRODUCTION

Respiratory syncytial virus (RSV) is an important pathogen in infants, children, older adults, and those with comorbidities. Mechanisms involving viral proteins appear to underly the ability of RSV to evade and modulate host immunity. We aimed to understand virus- and host-dependent factors regulating the development and severity of RSV infection, as relate to the prevention and treatment of RSV-associated disease in adults, through a systematic literature review (SLR).

METHODS

An SLR was conducted to identify immune mechanisms involved in the protective response to RSV infection in adults, and responses that may contribute to the development of severe disease. Concurrent searches (MEDLINE/Embase) using embase.com identified relevant papers published between 1990 and 19 April 2023.

RESULTS

Of 1813 records identified, 113 were selected for review. Inclusion criteria were based on relevant patient populations, outcomes, and study methodologies. RSV is common, recurrent, and associated with high morbidity and mortality in older adults and people with underlying chronic diseases. Immune responses differ between younger and older adults. The approval of effective vaccines may protect older individuals from symptomatic RSV infection.

CONCLUSIONS

We established the complexities of RSV immune response, but further research is required to fully understand anti-RSV immunology.

Binding and neutralising antibodies to respiratory syncytial virus and influenza A virus in serum and bronchoalveolar lavage fluid of healthy adults in the United States: A cross-sectional study

Using serum and bronchoalveolar lavage (BAL) fluid collected from 20 healthy adults (23-37 years, 55 % female) in the United States, we measured immunoglobulin (Ig) A, IgG, and neutralising activity against respiratory syncytial virus (RSV) and influenza A (H1N1) virus. RSV-binding IgA and IgG measurements in serum were positively correlated with those in BAL. For influenza A (H1N1) virus, serum and BAL IgA antibodies were positively correlated, whereas IgG antibodies did not show a significant correlation. RSV-specific and influenza A (H1N1)-specific neutralising activity did not correlate between serum and BAL samples. These results demonstrate virus-specific correlations between antibodies in the serum and BAL that may not necessarily reflect correlations in functional activity. Further work is needed to confirm our preliminary observations, and define the immune correlates of neutralising activity to these and other respiratory viruses in the lower respiratory tract.

Influential drivers of the cost-effectiveness of respiratory syncytial virus vaccination in European older adults: a multi-country analysis

BACKGROUND

We aimed to identify influential drivers of the cost-effectiveness of older adult respiratory syncytial virus (RSV) vaccination in Denmark, Finland, the Netherlands and Valencia-Spain.

METHODS

A static multi-cohort model was parameterised using country- and age-specific hospitalisations using three approaches: (A) the International Classification of Diseases (ICD)-coded hospitalisations, (B) laboratory RSV-confirmed hospitalisations and (C) time-series modelling (TSM). Plausible hypothetical RSV vaccine characteristics were derived from two protein subunit vaccines for adults aged ≥60 years. A full incremental analysis was conducted by comparing three RSV vaccination strategies: (1) in adults aged ≥60 years ("60y+"); (2) in adults aged ≥65 years ("65y+"); (3) in adults aged ≥75 years ("75y+") to "no intervention" and to each other. Both costs and quality-adjusted life-years (QALYs) were discounted at country-specific discount rates and the analysis was conducted from both the healthcare payers' and societal perspectives. Value of information, probabilistic sensitivity and scenario analyses identified influential drivers.

RESULTS

Besides vaccine price, the hospitalisation estimates were most influential: (A) Using adjusted RSV-ICD-coded hospitalisations at a vaccine price of €150 per dose, no intervention was cost-effective up to willingness-to-pay (WTP) values of €150,000 per QALY gained in Denmark and the Netherlands, and up to €124,000 per QALY gained in Finland. (B) Using the adjusted RSV-confirmed dataset, the findings were consistent in Denmark and comparable in Finland. In Spain-Valencia, the 75y+ strategy became cost-effective at WTP >€55,000. (C) Using TSM-based estimates, the 75y+ strategy was cost-effective at WTP >€45,000, >€101,000, >€41,000 and >€114,000 in Denmark, Finland, the Netherlands and Spain-Valencia, respectively. Sensitivity analyses showed that the (in-hospital) case fatality ratio and the specification of its age dependency were both influential. Duration of protection was found more influential than a variety of plausible waning patterns over the duration of protection.

CONCLUSIONS

Data gaps and uncertainties on the RSV-related burden in older adults persist and influence the cost-effectiveness of RSV vaccination. More refined age- and country-specific data on the RSV attributable burden are crucial to aid decision making.

Epidemiological and Clinical Characteristics of Adult RSV Infections: A Retrospective Analysis at University Hospital Center Zagreb (2022-2024)

Respiratory syncytial virus (RSV) is a significant cause of respiratory infections in adults, particularly among older adults and individuals with chronic diseases. While traditionally linked to pediatric populations, RSV's impact on adults, especially the elderly, is increasingly recognized but remains understudied in many regions. This retrospective study, conducted at the University Hospital Center Zagreb from October 2022 to April 2024, is the first to analyze RSV-positive adults in Croatia. Using RT-PCR testing, we evaluated clinical and epidemiological characteristics in both hospitalized and outpatient populations, focusing on those aged > 65 years. Among 2631 tested individuals, the RSV prevalence was 5.25%, with older adults experiencing the most severe outcomes, including pneumonia, COPD exacerbation, and intensive care admissions. Seasonal analysis confirmed a winter peak in RSV cases, while chronic conditions such as cardiovascular and respiratory diseases were strongly associated with higher complication rates. These findings demonstrate that older adults with comorbidities bear the greatest burden of RSV infection, highlighting the need for the early identification of high-risk patients. By providing detailed insights into RSV-related outcomes in this population, this study supports the development of targeted prevention and management strategies to reduce the burden of RSV in vulnerable groups.

Burden of Respiratory Syncytial Virus Disease in Adults with Asthma and Chronic Obstructive Pulmonary Disease: A Systematic Literature Review

PURPOSE OF REVIEW

Accumulating data indicate that asthma and chronic obstructive pulmonary disease (COPD) increase the risk of severe respiratory syncytial virus (RSV) infection. This systematic literature review assessed the burden of RSV disease among adults ≥ 18 years with asthma or COPD.

RECENT FINDINGS

Data on the prevalence of asthma or COPD among RSV-infected adults, RSV-related hospitalizations, complications, and mortality were collected from studies published between January 1, 2000 and November 28, 2023 in PubMed, Embase, and grey literature. All extracted data were analyzed descriptively. Pooled estimates of asthma or COPD prevalence among RSV-infected adults were calculated from generalized linear mixed effects model meta-analyses. Forty studies were included. The prevalence of asthma and COPD among RSV-infected adults was high, especially in inpatient settings with pooled estimates (95% confidence interval) of 19.3% (15.0-24.6) for asthma and 30.8% (26.1-36.0) for COPD. Adults with asthma or COPD were more likely to be hospitalized following RSV infection than those without these conditions. The incidence rate ratios of hospitalization were 2.0-3.6 (crude) and 6.7-8.2 (adjusted) for asthma and 3.2-13.4 (crude) and 9.6-9.7 (adjusted) for COPD. The most frequently reported RSV-related complications were exacerbation of asthma (up to 64.9%) and COPD (up to ≥ 83.0%). In-hospital case fatality rates were 2.6-4.3% (asthma) and 2.8-17.8% (COPD). These comprehensive data showing a high RSV disease burden in adults with asthma or COPD can be used to inform policy decisions around RSV vaccines and improve preventive care in this high-risk population.

The Potential Public Health Impact of the Adjuvanted Respiratory Syncytial Virus Prefusion F Protein Vaccine Among Older Adults in Italy

Background: Respiratory syncytial virus (RSV) is a common cause of acute respiratory infection (ARI). The risk of severe RSV outcomes is higher among older adults (OAs) and individuals with chronic diseases (high risk, HR). AS01E-adjuvanted RSV preFusion protein 3 OA vaccine (adjuvanted RSVPreF3 OA is approved for the prevention of lower respiratory tract disease [LRTD] due to RSV in OAs). The objective of this study was to assess the potential public health impact of an RSV vaccination program using adjuvanted RSVPreF3 OA in adults ≥75 years (y) and HR adults ≥60 y in Italy. Methods: A static multi-cohort Markov model was used to estimate the number of RSV cases and associated health outcomes projected in adults ≥75 y and HR adults ≥60 y with no RSV vaccination or with a single dose of adjuvanted RSVPreF3 OA. Epidemiological, healthcare resource use and cost data were obtained from the scientific literature. Vaccine efficacy and waning inputs were based on results from the AReSVi-006 phase III clinical trial. Several scenarios for vaccine coverage were explored. Results: Assuming the target vaccination rate for influenza vaccination in Italy (75%), the model predicted that vaccinating Italian adults ≥75 y and the HR population ≥ 60 y with adjuvanted RSVPreF3 OA would reduce the number of RSV-LRTD events by 43%, leading to a reduction in associated emergency department visits, hospitalizations, complications, deaths, and direct healthcare costs over a 3-year period. Conclusions: The vaccination of Italians aged ≥ 75 y and HR individuals aged ≥ 60 y using the adjuvanted RSVPreF3 OA vaccine has the potential to offer substantial public health benefits by reducing the burden of RSV disease.

Respiratory syncytial virus: Characteristics, complications and mortality in immunocompetent versus immunocompromised hospitalized adults in Northern Denmark

BACKGROUND

Respiratory syncytial virus (RSV) is an increasingly well-known cause of severe respiratory symptoms in adults. We aimed to describe characteristics, complications and in-hospital mortality of adults admitted to hospital with RSV-related respiratory symptoms.

METHODS

Data were collected from electronic health records in the North Denmark Region for hospitalized adults diagnosed with RSV between April 1st - December 31st 2021. We collected data on characteristics, complications and mortality. Results were compared between immunocompromised and -competent patients.

RESULTS

We included 111 patients. Sixty-five percent had comorbidities and 20 % received immunosuppressive drugs. Fifty-three percent had bacterial pneumonia and 61 % needed oxygen support. Mortality was 12 %. There were no differences in complications between the compared groups.

CONCLUSION

Severe respiratory symptoms were frequent among RSV-patients. Bacterial co-infections were common in the study population and mortality was considerable, regardless of known immunosuppression, thus warranting thorough and early investigations in RSV-positive patients.

Computable Phenotypes for Respiratory Viral Infections in the All of Us Research Program

Electronic health records (EHRs) contain rich temporal data about infectious diseases, but an optimal approach to identify infections remains undefined. Using the All of Us Research Program, we developed computable phenotypes for respiratory viruses by integrating billing codes, prescriptions, and laboratory results within 90-day episodes. Phenotypes computed from 265,222 participants yielded cohorts ranging from 238 (adenovirus) to 28,729 (SARS-CoV-2) cases. Virus-specific billing codes showed varied sensitivity (8-67%) and high positive predictive value (90-97%), except for influenza virus and SARS-CoV-2 where lower PPV (69-70%) improved with increasing billing codes. Identified infections exhibited expected seasonal patterns and virus proportions when compared with CDC data. This integrated approach identified episodic disease more effectively than individual components alone and demonstrated utility in identifying severe infections. The method enables large-scale studies of host genetics, health disparities, and clinical outcomes across episodic diseases.

Immunogenicity and safety of Ad26.RSV.preF/RSV preF protein vaccine at predicted intermediate- and end-of-shelf-life as an evaluation of potency throughout shelf life

This study assessed three Ad26.RSV.preF/RSV preF protein combinations, combining different Ad26.RSV.preF doses and naturally aged preF protein, representing the expected critical vaccine quality attributes close to release, around intermediate shelf-life (ISL) and near-presumed end-of-shelf-life (EoSL), as a way to evaluate the vaccine immunogenicity and safety throughout its shelf-life. A single dose of Ad26.RSV.preF/RSV preF protein vaccine was administered to adults 60-75 years of age. Solicited adverse events (AEs), unsolicited AEs, and serious AEs (SAEs) were assessed for 7-day, 28-day, and 6-month periods after vaccination, respectively. RSV preF-binding antibody concentrations and RSV neutralizing titers were measured 14 days post-vaccination as primary and secondary endpoints, respectively; binding antibodies were also measured 6 months post-vaccination. The RSV preF-binding antibody responses induced by Ad26.RSV.preF/RSV preF protein vaccine lots representing the critical quality attributes around ISL and near presumed EoSL were noninferior to the responses induced by the vaccine lot representing the critical quality attributes near release. The RSV preF-binding and RSV neutralizing antibody levels measured 14 days post-vaccination were similar across the 3 groups. RSV preF-binding antibody concentrations were also similar 6 months post-vaccination. Solicited AEs were mostly mild to moderate in intensity, and a decreased reactogenicity was observed from the Release group to the ISL and EoSL group. None of the reported SAEs were considered related to study vaccination. The study provided evidence of sustained immunogenicity and safety over the intended shelf-life of the Ad26.RSV.pref/RSV preF protein vaccine. The three vaccine lots had acceptable safety profiles.

Economic burden of cardiorespiratory hospitalizations associated with respiratory syncytial virus among United States adults in 2017-2019

Morbidity and mortality caused by respiratory syncytial virus (RSV) in older adults and those with underlying health conditions can be potentially alleviated through vaccination. To assist vaccine policy decision-makers and payers, we estimated the annual economic burden of RSV-associated cardiorespiratory hospitalizations among insured US adults aged ≥18 y in the Merative MarketScan claims database from September through August of 2017-2018 and 2018-2019. Negative binomial regression models were used to estimate the number of RSV-associated cardiorespiratory hospitalizations using MarketScan-identified cardiorespiratory diagnosis codes in the presence or absence of RSV circulation per weekly laboratory test positivity percentages from the Centers for Disease Control and Prevention. This number was multiplied by mean cardiorespiratory hospitalization costs to estimate total costs for RSV-associated cardiorespiratory hospitalizations. Number and cost for International Classification of Diseases (ICD)-coded RSV hospitalizations were quantified from MarketScan. In 2017-2018 and 2018-2019, respectively, 18,515,878 and 16,462,120 adults with commercial or Medicare supplemental benefits were assessed. In 2017-2018, 301,248 cardiorespiratory hospitalizations were observed; 0.32% had RSV-specific ICD codes, costing $44,916,324, and 5.52% were RSV-associated cardiorespiratory hospitalizations, costing $734,078,602 (95% CI: $460,826,580-$1,103,358,799). In 2018-2019, 215,525 cardiorespiratory hospitalizations were observed; 0.34% had RSV-specific ICD codes, costing $33,053,105, and 3.14% were RSV-associated cardiorespiratory hospitalizations, costing $287,549,472 (95% CI: $173,377,778-$421,884,259). RSV contributes to substantial economic burden of cardiorespiratory hospitalizations among US adults. Modeling excess risk using viral positivity data provides a comprehensive estimation of RSV hospitalization burden and associated costs, compared with relying on ICD diagnosis codes alone.

Incidence of RSV in Adults: A Comprehensive Review of Observational Studies and Critical Gaps in Information

BACKGROUND

We conducted a global comprehensive literature review of observational studies reporting respiratory syncytial virus (RSV) incidence in adults and determined current evidence gaps.

METHODS

PubMed and Embase were searched for English-language publications (2000-2022) and congress abstracts (2019-2021) reporting RSV incidence rates/cumulative incidence. Cross-sectional studies, case series, and other designs estimating only RSV frequency were excluded. The search included all geographic areas; data were extracted by age group and underlying condition where available.

RESULTS

In total, 528 potentially relevant records were identified, of which 37 primary studies were relevant to this review. Most evidence was from high-income regions. Approximately two-thirds of the studies reported RSV incidence in the hospital setting. Fifteen studies included or focused exclusively on RSV incidence in adult populations with underlying conditions. Studies varied in their measurement and presentation of incidence. RSV incidence estimates were highly variable within and between geographic regions. Overall, RSV incidence tended to increase with age and was highest in adults with underlying conditions.

CONCLUSIONS

Estimates of RSV incidence are highly variable across populations and geographies. Further population-based studies with well-defined, consistent case definitions and surveillance strategies are needed for accurate and comparable estimates of RSV incidence, particularly in the geographic regions identified by the gap analysis.

Relative Contribution of Diagnostic Testing to the Diagnosis of Respiratory Syncytial Virus in Hospitalized Adults in the United States

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of acute respiratory illness (ARI) in older adults. Optimizing diagnosis could improve understanding of RSV burden.

METHODS

We enrolled adults ≥50 years of age hospitalized with ARI and adults of any age hospitalized with congestive heart failure or chronic obstructive pulmonary disease exacerbations at 2 hospitals during 2 respiratory seasons (2018-2020). We collected nasopharyngeal (NP) and oropharyngeal (OP) swabs (n = 1558), acute and convalescent sera (n = 568), and expectorated sputum (n = 153) from participants, and recorded standard-of-care (SOC) NP results (n = 805). We measured RSV antibodies by 2 immunoassays and performed BioFire testing on respiratory specimens.

RESULTS

Of 1558 eligible participants, 92 (5.9%) tested positive for RSV by any diagnostic method. Combined NP/OP polymerase chain reaction (PCR) testing yielded 58 positives, while separate NP and OP testing identified 11 additional positives (18.9% increase). Compared to study NP/OP PCR alone, the addition of paired serology increased RSV detection by 42.9% (28 vs 40) among those with both specimen types, while the addition of SOC swab PCR increased RSV detection by 25.9% (47 vs 59).

CONCLUSIONS

The addition of paired serology testing, SOC swab results, and separate testing of NP and OP swabs improved RSV diagnostic yield in hospitalized adults.

Annual public health and economic burden of medically attended respiratory syncytial virus illnesses among US adults

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract disease (LRTD) among adults and can lead to serious morbidity and mortality; however, evidence on the magnitude of the public health and economic burden of adult RSV-LRTD is limited. This study was undertaken to project annual clinical outcomes and economic costs of medically attended RSV-LRTD among US adults, and to identify subgroups responsible for a disproportionate share of disease burden.

METHODS

Clinical outcomes of RSV-LRTD were projected for subgroups of US adults defined by age and comorbidity profile (with vs. without chronic/immunocompromising medical conditions) based on corresponding population sizes, episode (disease) rates, and case-fatality rates. Economic costs comprised medical (i.e., direct) costs and non-medical (i.e., indirect) costs of RSV-LRTD, and were generated based on numbers of episodes and unit costs in relation to setting of care, age, and comorbidity profile.

RESULTS

Among 265 million US adults aged ≥18 years in 2023, 6.5 million medically attended episodes of RSV-LRTD were projected to occur including 349,260 requiring hospitalization, 357,892 requiring an emergency department visit (not leading to hospitalization), and 5.8 million requiring other ambulatory care. Direct costs ($15.2 billion) and indirect costs ($9.7 billion) were projected to total $25.0 billion. Persons aged 60-99 years accounted for 31 % of the adult population and over 50 % of the economic burden of RSV-LRTD, while adults aged <60 years with chronic/immunocompromising medical conditions accounted for 10 % of the population and 27 % of the economic burden.

CONCLUSIONS

Annual burden of RSV-LRTD among US adults-especially older adults and those of all ages with underlying medical conditions-is substantial. Preventive measures, such as recently approved RSV vaccines, have the potential to yield important improvements in public and patient health, and to reduce the economic burden of RSV-LRTD from the US healthcare system and societal perspectives.

Humoral Immunogenicity of mRNA-1345 RSV Vaccine in Older Adults

BACKGROUND

The mRNA-1345 vaccine demonstrated efficacy against respiratory syncytial virus (RSV) disease with acceptable safety in adults aged ≥60 years in the ConquerRSV trial. Here, humoral immunogenicity results from the trial are presented.

METHODS

This phase 2/3 trial randomly assigned adults (≥60 years) to mRNA-1345 50-µg encoding prefusion F (preF) glycoprotein (n = 17 793) vaccine or placebo (n = 17 748). RSV-A and RSV-B neutralizing antibody (nAb) and preF binding antibody (bAb) levels at baseline and day 29 postvaccination were assessed in a per-protocol immunogenicity subset (PPIS; mRNA-1345, n = 1515; placebo, n = 333).

RESULTS

Day 29 nAb geometric mean titers (GMTs) increased 8.4-fold against RSV-A and 5.1-fold against RSV-B from baseline. Seroresponses (4-fold rise from baseline) in the mRNA-1345 groups were 74.2% and 56.5% for RSV-A and RSV-B, respectively. Baseline GMTs were lower among participants who met the seroresponse criteria than those who did not. mRNA-1345 induced preF bAbs at day 29, with a pattern similar to nAbs. Day 29 antibody responses across demographic and risk subgroups were generally consistent with the overall PPIS.

CONCLUSIONS

mRNA-1345 enhanced RSV-A and RSV-B nAbs and preF bAbs in adults (≥60 years) across various subgroups, including those at risk for severe disease, consistent with its demonstrated efficacy in the prevention of RSV disease.

CLINICAL TRIALS REGISTRATION

NCT05127434.

Respiratory Syncytial Virus vs Influenza Virus Infection: Mortality and Morbidity Comparison Over 7 Epidemic Seasons in an Elderly Population

BACKGROUND

Respiratory syncytial virus (RSV) infection is gaining interest due to the recent development of vaccines but is still misdiagnosed in the elderly. The primary objective was to compare all-cause mortality at day 30. Secondary objectives were to compare clinical presentation and rates of consolidative pneumonia, hospitalization, and intensive care unit (ICU) admission.

METHODS

A single-center retrospective study was conducted in a French university hospital during 7 epidemic seasons including 558 patients aged ≥75 years: 125 with RSV and 433 with influenza (median age, 84.8 years).

RESULTS

Patients with RSV had more respiratory symptoms (wheezing, dyspnea) whereas patients with influenza had more general symptoms (fever, asthenia, myalgia). The following were higher in the RSV group: consolidative pneumonia (28.8% vs 17.2%, P = .004), hospitalization (83.2% vs 70%, P = .003), ICU admission (7.2% vs 3.0%, P = .034), and length of stay (median [IQR], 9 days [2-16] vs 5 days [0-12]; P = .002). Mortality rates at day 30 were comparable (9.6% vs 9.7%, P = .973).

CONCLUSIONS

This study included the largest cohort of patients infected with RSV aged >75 years documented in-depth thus far. RSV shares a comparable mortality rate with influenza but is associated with higher rates of consolidative pneumonia, hospitalization, ICU admissions, and extended hospital stays.

Integrated untargeted and targeted lipidomics discovers LPE 16:0 as a protector against respiratory syncytial virus infection

Respiratory Syncytial Virus (RSV) is a leading cause of acute lower respiratory infections, imposing a substantial burden on healthcare systems globally. While lipid disorders have been observed in the lungs of infants and young children with RSV pneumonia, the specific characterization of these lipids and their roles in the development and progression of RSV pneumonia remain largely unexplored. To address this tissue, we established a non-targeted high-resolution lipidomics platform using UHPLC-Q-Exactive-MS to analyze lipid profiles in bronchoalveolar lavage fluid (BALF) obtained from mice infected with RSV. Through the lipidomics analysis, a total of 72 lipids species were identified, with 40 lipids were significantly changed. Notably, the primary changes were observed in ether phospholipids and lysophospholipids. Furthermore, a targeted lipidomics analysis utilizing UHPLC-QQQ-MS/MS was developed to specifically assess the levels of lysophospholipids, including lysophosphocholine 16:0 (LPC 16:0), lysophosphoethanolamine 16:0 (LPE 16:0) and lysophosphoglycerol 16:0 (LPG 16:0), in RSV-infected mice compared to control mice. Animal experiments revealed that LPE 16:0, rather than LPC 16:0 or LPG 16:0, provided protection against RSV-induced weight loss, reduced lung viral load, regulated immune cells and mitigated lung injury in mice afflicted with RSV pneumonia. In summary, our findings suggested that the host responses to RSV infection pathology are closely with various lipid metabolic. Additionally, our results elucidated novel biological functions of LPE 16:0 and offering new avenues for drug development against RSV pneumonia.

Real-World Assessment of Economic and Clinical Outcomes in Thai Patients With Respiratory Syncytial Virus Infection Across Age Groups: A Retrospective Cohort Analysis

BACKGROUND

Respiratory syncytial virus (RSV) is an important cause of acute lower respiratory infections worldwide, including Thailand. This study aimed to assess clinical and economic burdens of RSV infections across different age groups in Thailand.

METHOD

A retrospective cohort study was conducted using data from a tertiary care hospital from 2014 to 2021. Patients who tested at least one positive RSV were included and stratified into five age groups (< 2, 2-5, 5-18, 18-65, and > 65 years). Healthcare resource utilization, direct medical costs, and clinical outcomes were analyzed with descriptive statistics. Generalized linear models with gamma distributions and log link were used to model cost outcomes. Costs were reported in 2021 US dollars (USD), with 1 USD = 31.98 Thai Baht.

RESULTS

A total of 2122 RSV-positive patients were identified, half of which (1097) were hospitalized. The median (interquartile range [IQR]) total hospitalization costs ranged from USD780 (IQR: USD488-USD1185) in those < 2 years to USD2231 (IQR: USD1250-USD4989) in those aged 65+ years. Case fatality rates among hospitalized patients also varied from 2.5% to 28.4% depending on age. Increased age, presence of comorbidities, and need for critical care were associated with higher hospitalization costs.

CONCLUSION

Among RSV-positive patients, younger children experienced the greatest burden, but poorer outcomes were observed in older adults. Higher costs were associated with older age, comorbidities and critical care needs. Understanding RSV economic burdens is crucial for assessing the cost-effectiveness and public health value of vaccination programs that prioritize at-risk groups to mitigate the public health impact.

Safety and immunogenicity of an mRNA-based RSV vaccine in Japanese older adults aged ≥60 years: A phase 1, randomized, observer-blind, placebo-controlled trial

BACKGROUND

Respiratory syncytial virus (RSV) represents a global health concern, including in older adults. This study assessed the safety and immunogenicity of mRNA-1345, an investigational mRNA RSV vaccine, in adults aged ≥60 years of Japanese descent.

METHODS

In this phase 1, randomized, observer-blind, placebo-controlled study, participants were randomized to receive one injection of mRNA-1345 100 μg or placebo. Solicited local and systemic adverse reactions (ARs) were collected within 7 days following injection. Unsolicited adverse events (AEs) were collected up to 28 days after injection; AEs of special interest, medically attended AEs, and serious AEs were collected through end of study. Immunogenicity was assessed at baseline and months 1, 2, 3, and 6 following injection.

RESULTS

Twenty-five adults of Japanese descent aged ≥60 years received one injection of mRNA-1345 100 μg (n = 21) or placebo (n = 4). mRNA-1345 was well-tolerated; the most common local and systemic solicited ARs were injection site pain, and fatigue and myalgia, respectively, which were generally mild to moderate and transient. No serious AEs were reported. Neutralizing (nAb) and binding (bAb) antibodies were detectable at baseline, consistent with prior RSV exposure. mRNA-1345 boosted RSV nAb titers and preF bAb concentrations 1 month post-injection (geometric mean fold rise: RSV-A nAb, 11.2; RSV-B nAb, 6.6; preF bAb, 9.1). Titers among mRNA-1345 recipients remained above baseline through 6 months.

CONCLUSIONS

mRNA-1345 100 μg was well-tolerated among older adults of Japanese descent and induced nAbs and bAbs which were durable through 6 months, supporting its continued development.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04528719.

Serum and mucosal antibody-mediated protection and identification of asymptomatic respiratory syncytial virus infection in community-dwelling older adults in Europe

Introduction

Respiratory syncytial virus (RSV) causes acute respiratory tract infection (ARTI) and reinfects adults throughout life, posing a risk for hospitalization in older adults (>60 years) with frailty and comorbidities.

Methods

To investigate serum and mucosal antibodies for protection against RSV infections, baseline serum samples were compared for RSV-pre- and -post-fusion (F) binding, and RSV-A2 neutralizing IgG antibodies between symptomatic RSV-ARTI (N = 30), non-RSV (RSV negative) ARTI (N = 386), and no ARTI (N = 338). Mucosal RSV-pre-F IgA and IgG levels, as well as serum RSV-G IgG antibodies, were analyzed to determine their association with protection from symptomatic RSV-ARTI in a subset study.

Results

Using a receiver operating characteristic (ROC) analysis, we established thresholds of 1.4- to 1.6-fold change (FC) for RSV-pre-F and -post-F, and RSV-A2 neutralizing IgG antibodies, respectively, enabling the identification of asymptomatic RSV cases with high sensitivity and specificity (>80% and >90%, respectively). As a result, serum RSV-pre-F, RSV-G IgG, and mucosal pre-F binding IgA antibodies showed correlations with protection against symptomatic RSV infection. RSV-pre-F IgG antibodies were correlated with protection from RSV infections irrespective of the symptoms.

Discussion

This study provides insights into antibody-mediated protection for symptomatic RSV infection in a community-dwelling older-adult population and establishes a threshold to identify asymptomatic RSV infection using a data-driven approach.

Respiratory Syncytial Virus-related Community Chronic Obstructive Pulmonary Disease Exacerbations and Novel Diagnostics: A Binational Prospective Cohort Study

Rationale: Respiratory syncytial virus (RSV) is a common global respiratory virus that is increasingly recognized as a major pathogen in frail older adults and as a cause of chronic obstructive pulmonary disease (COPD) exacerbations. There is no single test for RSV in adults that has acceptable diagnostic accuracy. Trials of RSV vaccines have recently shown excellent safety and efficacy against RSV in older adults; defining the frequency of RSV-related community infections and COPD exacerbations is important for vaccine deployment decisions. Objectives: This prospective study aimed to establish the frequency of outpatient-managed RSV-related exacerbations of COPD in two well-characterized patient cohorts using a combination of diagnostic methods. Methods: Participants were recruited at specialist clinics in London, United Kingdom, and Groningen, the Netherlands, beginning in 2017 and observed for three consecutive RSV seasons, during exacerbations, and at least twice yearly. RSV infections were detected by RT-PCR and serologic testing. Measurements and Main Results: A total of 377 patients with COPD attended 1,999 clinic visits and reported 310 exacerbations. There were 27 RSV-related exacerbations (8.7% of the total); of these, seven were detected only by PCR, 16 only by serology, and four by both methods. Increases in RSV-specific Nucleoprotein antibody were as sensitive as those in the antibody to Pre-Fusion or Post-Fusion for serodiagnosis of RSV-related exacerbations. Conclusions: RSV is associated with 8.7% of outpatient-managed COPD exacerbations in this study. Antibodies to RSV Nucleoprotein may have diagnostic value and are potentially important in a vaccinated population. The introduction of vaccines that prevent RSV is expected to benefit patients with COPD.

Induction of neutralizing antibody responses by AAV5-based vaccine for respiratory syncytial virus in mice

Introduction

Respiratory Syncytial Virus (RSV) is a significant cause of respiratory illnesses worldwide, particularly in infants and elderly individuals. Despite the burden RSV imposes, effective preventive measures are limited. The research application of adeno-associated virus (AAV) in vaccine platforms has been expanding, and its potential in prevention and treatment has garnered much attention.

Methods

In this study, we explored the potential application of a recombinant adeno-associated virus 5 (rAAV5) vector-based RSV vaccine, focusing on the expression of the pre-fusion (Pre-F) protein structure. Through intramuscular immunization in mice. The immunogenicity of the vaccine was evaluated in Balb/c mice immunized intramuscularly and intranasal, respectively.

Results

The rAAV5-RSV-Fm vaccine demonstrated positive humoral and induced antibody titers against RSV strains A and B for up to 120 days post-immunization. Notably, intranasal administration also elicited protective antibodies. Characterization studies confirmed the ability of the vac-cine to express the Pre-F protein and its superior immunogenicity compared to that of full-length F protein.

Conclusion

These findings underscore the potential application of rAAV5 vector platforms in RSV vaccine development and further investigation into their protective efficacy is warranted.

A multi-center study on genetic variations in the fusion protein of respiratory syncytial virus from children with Acute Lower Respiratory Tract Infections in China during 2017-2021

Respiratory syncytial virus (RSV) is a significant cause of acute lower respiratory tract infection (ALRTI) in children under five years of age. Between 2017 and 2021, 396 complete sequences of the RSV F gene were obtained from 500 RSV-positive throat swabs collected from ten hospitals across nine provinces in China. In addition, 151 sequences from China were sourced from GenBank and GISAID, making a total of 549 RSV F gene sequences subjected to analysis. Phylogenetic and genetic diversity analyses revealed that the RSV F genes circulating in China from 2017 to 2021 have remained relatively conserved, although some amino acids (AAs) have undergone changes. AA mutations with frequencies ≥ 10% were identified at six sites and the p27 region: V384I (site I), N276S (site II), R213S (site Ø), and K124N (p27) for RSV A; F45L (site I), M152I/L172Q/S173 ​L/I185V/K191R (site V), and R202Q/I206M/Q209R (site Ø) for RSV B. Comparing mutational frequencies in RSV-F before and after 2020 revealed minor changes for RSV A, while the K191R, I206M, and Q209R frequencies increased by over 10% in RSV B. Notably, the nirsevimab-resistant mutation, S211N in RSV B, increased in frequency from 0% to 1.15%. Both representative strains aligned with the predicted RSV-F structures of their respective prototypes exhibited similar conformations, with low root-mean-square deviation values. These results could provide foundational data from China for the development of RSV mAbs and vaccines.

Respiratory syncytial virus infections in adults: a narrative review

Respiratory syncytial virus (RSV), an RNA virus spread by droplet infection that affects all ages, is increasingly recognised as an important pathogen in adults, especially among older people living with comorbidities. Distinguishing RSV from other acute viral infections on clinical grounds alone, with sufficient precision to be clinically useful, is not possible. The reference standard diagnosis is by PCR: point-of-care tests perform less well with lower viral loads. Testing samples from a single respiratory tract site could result in underdetection. RSV is identified in 6-11% of outpatient respiratory tract infection (RTI) consultations in older adults (≥60 years, or ≥65 years, depending on the study) and accounts for 4-11% of adults (≥18 years) hospitalised with RTI, with 6-15% of those hospitalised admitted to intensive care, and 1-12% of all adults hospitalised with RSV respiratory tract infection dying. Community-based studies estimate the yearly incidence of RSV infection at around 3-7% in adults aged 60 years and older in high-income countries. Although RSV accounts for a similar disease burden as influenza in adults, those hospitalised with severe RSV disease are typically older (most ≥60 years) and have more comorbidities, more respiratory symptoms, and are frequently without fever. Long-term sequelae are common and include deterioration of underlying disease (typically heart failure and COPD). There are few evidence-based RSV-specific treatments currently available, with supportive care being the main modality. Two protein subunit vaccines for protection from severe RSV in adults aged 60 years and older were licensed in 2023, and a third-an mRNA-based vaccine-recently gained market approval in the USA. The phase 3 studies in these three vaccines showed good protection against severe disease. Data on real-world vaccine effectiveness in older adults, including subgroups at high risk for RSV-associated hospitalisation, are needed to establish the best use of these newly approved RSV vaccines. New diagnostics and therapeutics are being developed, which will also need rigorous evaluation within their target populations to ensure they are used only for those in whom there is evidence of improved outcomes. There is an urgent need to reconceptualise this illness from one that is serious in children, but far less important than influenza in older people, to thinking of RSV as also a major risk to health for older people that needs targeted prevention and treatment.

Burden of Respiratory Syncytial Virus (RSV) Infection Among Adults in Nursing and Care Homes: A Systematic Review

BACKGROUND

Older adults in nursing and care homes (NCHs) are vulnerable to severe respiratory syncytial virus (RSV) infection, hospitalization, and death. This study aimed to gather data on RSV disease among older adults in NCHs and identify reported risk factors for RSV hospitalization and case fatality.

METHODS

The study protocol was registered in PROSPERO (CRD42022371908). We searched MEDLINE, EMBASE, and Global Health databases to identify articles published between 2000 and 2023. Observational and experimental studies conducted among older adults in NCHs requiring assistive care and reporting RSV illness were included and relevant data were extracted.

RESULTS

Of 18,690 studies screened, 32 were selected for full-text review, and 20 were included. Overall, the number of NCH residents ranged from 42 to 1459 with a mean age between 67.6 and 85 years. Attack rates ranged from 6.7% to 47.6% and annual incidence ranged from 0.5% to 14%. Case fatality rates ranged from 7.7% to 23.1%. We found similar annual incidence rates of RSV-positive acute respiratory infection (ARI) of 4582 (95% CI: 3259-6264) and 4785 (95% CI: 2258-10,141) per 100,000 reported in two studies. Annual incidence rate of RSV-positive lower respiratory tract infection was 3040 (95% CI: 1986-4454) cases per 100,000 adults. Annual RSV-ARI hospital admission rates were between 600 (95% CI: 190-10,000) and 1104 (95% CI: 350-1930) per 100,000 person-years. Among all RSV disease cases, commonly reported chronic medical conditions included chronic obstructive pulmonary disease (COPD), heart failure, ischemic heart disease, coronary artery disease, hypertension, diabetes, kidney dysfunction, cerebrovascular accident, malignancies, dementia, and those with a Charlson comorbidity score > 6.5.

CONCLUSION

Data on RSV infection among NCH residents are limited and largely heterogeneous but document a high risk of illness, frequent hospitalization, and high mortality. Preventive interventions, such as vaccination, should be considered for this high-risk population. Nationally representative epidemiologic studies and NCH-based viral pathogen surveillance could more precisely assess the burden on NCH residents.

Cold-adapted influenza vaccine carrying three repeats of a respiratory syncytial virus (RSV) fusion glycoprotein epitope site protects BALB/c mice and cotton rats against RSV infection

Respiratory syncytial virus is the major cause of respiratory viral infections, particularly in infants, immunocompromised populations, and the elderly (over 65 years old), the prevention of RSV infection has become a priority. In this study, we generated a chimeric influenza virus, termed LAIV/RSV/HA-3F, using reverse genetics technology which contained three repeats of the RSV fusion protein neutralizing epitope site II to the N terminal in the background of the hemagglutinin (HA) gene of cold adapted influenza vaccine A/California/7/2009 ca. LAIV/RSV/HA-3F exhibited cold-adapted (ca) and attenuated (att) phenotype. BALB/c mice immunized intranasally with LAIV/RSV/HA-3F showed robust immunogenicity, inducing viral-specific antibody responses against both influenza and RSV, eliciting RSV-specific humoral, cellular and mucosal immune responses. LAIV/RSV/HA-3F also conferred protection as indicated by reduced viral titers and improved lung histopathological alterations against live RSV virus challenge. Mechanismly, single-cell RNA sequencing (scRNA-seq) and single-cell T cell antigen receptor (TCR) sequencing were employed to characterize the immune responses triggered by chimeric RSV vaccine, displaying that LAIV/RSV/HA-3F provided protection mainly via interferon-γ (IFN-γ). Moreover, we found that LAIV/RSV/HA-3F significantly inhibited viral replication in the challenged lung and protected against subsequent RSV challenge in cotton rats without causing lung disease. Taken together, our findings demonstrated that LAIV/RSV/HA-3F has potential as a promising bivalent vaccine with dual purpose candidate for the prevention of influenza and RSV, and preclinical and clinical studies warrant further investigations.

Altered epidemiological patterns of Respiratory Syncytial Virus and influenza detections in a tropical Australian setting 2020 to 2023

BACKGROUND

We describe the recent temporal patterns of respiratory syncytial virus (RSV) and influenza virus detections in the Northern Territory (NT) of Australia, between 2020 and 2023.

METHODS

This retrospective analysis of patients presenting with respiratory diseases utilised a multiplex viral nucleic acid detection assay for RSV, influenza and SARS Cov2 (COVID-19) to determine the relative frequency of non-COVID-19 respiratory viral detections by age and month during the study period.

RESULTS

During this period of the NT COVID-19 epidemic, disruption of the usual annual wet season RSV outbreak patterns occurred, and the yearly influenza peak was absent for two annual cycles. Our data also reveals that 25% of RSV infections were occurring in patients greater than 40 years of age, compared to 32% of influenza infections presenting in the same period, documenting a greater burden of adult disease than previously documented in the NT.

CONCLUSIONS

Loss of non-COVID-19 viral seasonality and a substantial unrecognised RSV adult burden were noted. We will continue to monitor seasonality, and the RSV burden and this will help to target the populations benefiting from recently released RSV vaccine.

Proof of stability of an RSV Controlled Human Infection Model challenge agent

In 2018, SGS Belgium NV developed RSV-NICA (Respiratory Syncytial Virus-Nasobronchial Infective Challenge Agent), an RSV type A challenge agent for use in RSV Controlled Human Infection Model (CHIM) studies.It is widely recognized that the stability of RSV can be influenced by a variety of environmental parameters, such as temperature and pH. Consequently, our objective was to evaluate the stability of the viral titer of RSV-NICA following five years of controlled storage and to determine the uniformity of the viral titers across different vials of a GMP-qualified batch of RSV-NICA. In addition, we examined the capacity of RSV-NICA to infect human primary airway epithelial cells (MucilAir™), the principal target cells of RSV, and evaluated the influence of single and recurrent freeze-thaw cycles on the infectious viral titer of the challenge agent.The aliquoted RSV-NICA virus stock was subjected to standard virological and molecular methods to gather data on the titer and consistency of the viral titer contained within 24 representative vials of the stock. Our findings illustrate that over a span of five years of cryo-storage, the infectious viral titer in 75% of the tested vials exhibited a comparable average infectious viral titer (4.75 ± 0.06 vs 4.99 ± 0.11; p-value = 0.14). A considerable reduction down to an undetectable level of infectious virus was observed in the remaining vials. RSV-NICA demonstrated its capacity to effectively infect differentiated human airway epithelial cells, with active virus replication detected in these cells through increasing RSV genome copy number over time. Virus tropism for ciliated cells was suggested by the inhibition of cilia beating coupled with an increase in viral RNA titers. No discernable impact on membrane barrier function of the epithelial lung tissues nor cytotoxicity was detected. Pooling of vials with infectious titers > 4.0 log10 TCID50/ml and freeze-thawing of these combined vials showed no deterioration of the infectious titer. Furthermore, pooling and re-aliquoting of vials spanning the entire range of viral titers (including vials with undetectable infectious virus) along with subjecting the vials to three repeated freeze-thaw cycles did not result in a decrease of the infectious titers in the tested vials.Taken together, our findings indicate that long-term cryo-storage of vials containing RSV-NICA challenge agent may influence the infectious viral titer of the virus, leading to a decrease in the homogeneity of this titer throughout the challenge stock. However, our study also demonstrates that when heterogeneity of the infectious titer of an RSV stock is observed, rounds of pooling, re-aliquoting and subsequent re-titration serve as an effective method not only to restore the homogeneity of the infectious titer of an RSV-A stock, but also to optimize patient-safety, scientific and operational aspects of viral inoculation of study participants during at least the period of one RSV CHIM trial. RSV-NICA is a stable, suitable CHIM challenge agent that can be utilized in efficacy trials for RSV vaccines and antiviral entities.

Efficacy of Respiratory Syncytial Virus Vaccination to Prevent Lower Respiratory Tract Illness in Older Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

A systematic review and meta-analysis was designed in order to ascertain the effectiveness of respiratory syncytial virus (RSV) vaccination in preventing lower respiratory tract diseases (LRTD) in older adults (age ≥ 60 years). Studies reporting on randomized controlled trials (RCTs) were searched for in three databases (PubMed, Embase, and Scopus) and the preprint repository medRxiv until 31 March 2024. A total of nine studies were eventually included, two of which were conference proceedings. Our analysis included five RCTs on five RSV vaccines (RSVpreF, RSVPreF3, Ad26.RSV.preF, MEDI7510, and mRNA-1345). The meta-analysis documented a pooled vaccine efficacy of 81.38% (95% confidence interval (95% CI) 70.94 to 88.06) for prevention of LRTD with three or more signs/symptoms during the first RSV season after the delivery of the vaccine. Follow-up data were available for RSVPreF3 (2 RSV seasons), RSVpreF (mid-term estimates of second RSV season), and mRNA-1345 (12 months after the delivery of the primer), with a pooled VE of 61.15% (95% CI 45.29 to 72.40). After the first season, the overall risk for developing RSV-related LRTD was therefore substantially increased (risk ratio (RR) 4.326, 95% CI 2.415; 7.748). However, all estimates were affected by substantial heterogeneity, as suggested by the 95% CI of I2 statistics, which could be explained by inconsistencies in the design of the parent studies, particularly when dealing with case definition. In conclusion, adult RSV vaccination was quite effective in preventing LRTD in older adults, but the overall efficacy rapidly decreased in the second season after the delivery of the vaccine. Because of the heterogenous design of the parent studies, further analyses are required before tailoring specific public health interventions.

Respiratory syncytial virus-related hospital stays in adults in France from 2012 to 2021: A national hospital database study

BACKGROUND

Respiratory syncytial virus (RSV) causes lower respiratory tract infections (LRTI) that may lead to hospitalization or death. The present study aimed to assess the burden of RSV infections in hospitalized adults.

METHODS

RSV-related hospitalizations were identified from the nationwide hospital claims database in France (PMSI) from 2012 to 2021 using ICD-10 codes J12.1, J20.5, J21.0 or B97.4, and outcomes assessment focused on 2016-2020. In-hospital outcomes included length of stay, need for intensive care (ICU) and in-hospital all-cause mortality. Post-discharge outcomes included 30-day readmission for decompensation, 90-day RSV-related readmission, and 30 and 60-day in-hospital mortality.

RESULTS

A cumulated number of 17 483 RSV-related stays were identified representing a rate of 72.0 cases per million stays. The outcomes assessment included 12,987 patients: 55.8 % were females and the mean age was 74.1 ± 16.4 years, with 57 % ≥ 75 years. Most of patients (78.6 %) had at least one comorbidity, mainly chronic respiratory (56.3 %) and cardiovascular diseases (41.3 %), or diabetes (23.5 %). A co-infection was found in 22.4 %, primarily bacterial (12 %). The mean length of stay was 12.3 ± 13.1 days. Overall, 10.9 % were admitted to an ICU and in-hospital mortality was 7.3 %. In-hospital outcomes were higher in cases of co-infection. Among 12 033 patients alive at discharge from the index stay, 6.5 % were readmitted with RSV within 90 days, 8.1 % for decompensation within 30 days, and 5.6 % died within 60-day.

CONCLUSION

This study demonstrated the high burden of RSV infections in older adults and those with chronic conditions, and the need for preventive strategies.

The disease burden of respiratory syncytial virus in older adults

PURPOSE OF REVIEW

To highlight the respiratory syncytial virus (RSV) disease burden and the current developments and challenges in RSV prevention for older adults ≥60 years through analysis of RSV epidemiology and the effectiveness of emerging vaccines.

RECENT FINDINGS

In industrialized countries, RSV incidence rates and hospitalization rates among older adults are estimated to be 600.7 cases per 100 000 person-years and 157 hospitalizations per 100 000 person-years, respectively. Yet, accurately determining RSV morbidity and mortality in older adults is challenging, thus resulting in substantially under-estimating the disease burden. The in-hospital fatality rates vary substantially with age and geographies, and can be as high as 9.1% in developing countries. Two promising RSV vaccines for the elderly have been approved, demonstrating efficacies of up to 94.1%, signifying considerable advancement in RSV prevention. However, concerns over potential side effects remain.

SUMMARY

RSV is associated with a significant burden in older adults. While the landscape of RSV prevention in older adults is promising with the licensure of vaccines from two companies, current trial data underscore the need for additional studies. Addressing the real-world effectiveness of these vaccines, understanding potential rare side effects, and ensuring broad inclusivity in future trials are crucial steps to maximize their potential benefits.

From Forgotten Pathogen to Target for New Vaccines: What Clinicians Need to Know about Respiratory Syncytial Virus Infection in Older Adults

Respiratory syncytial virus (RSV) is increasingly recognized as being implicated in acute illness in older adults, with a significant weight in hospitalizations for respiratory illness and death. By means of a best-evidence review, this paper aims to investigate whether RSV can be considered a forgotten pathogen in older patients, looking at trends in the literature volume and exploring possible epidemiological and clinical features underlying the focus given to it. We then present an assessment of its disease burden and present and future strategies for its reduction, particularly in light of the recent availability of new vaccines.

Targeted metagenomics reveals association between severity and pathogen co-detection in infants with respiratory syncytial virus

Respiratory syncytial virus (RSV) is the leading cause of hospitalisation for respiratory infection in young children. RSV disease severity is known to be age-dependent and highest in young infants, but other correlates of severity, particularly the presence of additional respiratory pathogens, are less well understood. In this study, nasopharyngeal swabs were collected from two cohorts of RSV-positive infants <12 months in Spain, the UK, and the Netherlands during 2017-20. We show, using targeted metagenomic sequencing of >100 pathogens, including all common respiratory viruses and bacteria, from samples collected from 433 infants, that burden of additional viruses is common (111/433, 26%) but only modestly correlates with RSV disease severity. In contrast, there is strong evidence in both cohorts and across age groups that presence of Haemophilus bacteria (194/433, 45%) is associated with higher severity, including much higher rates of hospitalisation (odds ratio 4.25, 95% CI 2.03-9.31). There is no evidence for association between higher severity and other detected bacteria, and no difference in severity between RSV genotypes. Our findings reveal the genomic diversity of additional pathogens during RSV infection in infants, and provide an evidence base for future causal investigations of the impact of co-infection on RSV disease severity.

Epidemiology and Disease Burden of Respiratory Syncytial Virus Infection in Adults

Respiratory syncytial virus (RSV) constitutes a significant cause of respiratory illness and mortality among older adults, a demographic that is expanding with considerable impact on healthcare systems worldwide. The actual burden of RSV in this population may still be underestimated, owing to factors such as low awareness and suboptimal diagnostic sensitivity in adults, the lack of robust RSV surveillance systems, and the infrequent use of diagnostic testing. Recent advancements in respiratory virus detection have spurred further exploration into appropriate preventive and therapeutic strategies. The recent approval of two vaccines highlights the critical need for the precise estimation of the RSV disease burden to optimize the effectiveness and cost-efficiency of immunization programs. This narrative review aimed to summarize the existing knowledge of the RSV burden in adults with a particular focus on older adults, incorporating data from Korea. Overall, current estimates indicate that the annual RSV attack rate in the general adult population ranges from 1 - 7%, increasing to approximately 4 - 10% among elderly and high-risk groups. The in-hospital mortality rate can be estimated to be around 7 - 10%, rising up to 40% among intensive care unit-admitted patients. To elucidate RSV's disease burden, further continuing research, including population-based studies, is necessary.

Respiratory Syncytial Virus Vaccination Recommendations for Adults Aged 60 Years and Older: The NeumoExperts Prevention Group Position Paper

Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in adults, particularly older adults and those with underlying medical conditions. Vaccination has emerged as a potential key strategy to prevent RSV-related morbidity and mortality. This Neumoexperts Prevention (NEP) Group scientific paper aims to provide an evidence-based positioning and RSV vaccination recommendations for adult patients. We review the current literature on RSV burden and vaccine development and availability, emphasising the importance of vaccination in the adult population. According to our interpretation of the data, RSV vaccines should be part of the adult immunisation programme, and an age-based strategy should be preferred over targeting high-risk groups. The effectiveness and efficiency of this practice will depend on the duration of protection and the need for annual or more spaced doses. Our recommendations should help healthcare professionals formulate guidelines and implement effective vaccination programmes for adult patients at risk of RSV infection now that specific vaccines are available.

Respiratory Syncytial Virus, Influenza and SARS-CoV-2 in Homeless People from Urban Shelters: A Systematic Review and Meta-Analysis (2023)

Homeless people (HP) are disproportionally affected by respiratory disorders, including pneumococcal and mycobacterial infections. On the contrary, more limited evidence has been previously gathered on influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and very little is known about the occurrence of human respiratory syncytial virus (RSV), a common cause of respiratory tract infections among children and the elderly. The present systematic review was designed to collect available evidence about RSV, influenza and SARS-CoV-2 infections in HP, focusing on those from urban homeless shelters. Three medical databases (PubMed, Embase and Scopus) and the preprint repository medRxiv.org were therefore searched for eligible observational studies published up to 30 December 2023, and the collected cases were pooled in a random-effects model. Heterogeneity was assessed using the I2 statistics. Reporting bias was assessed by funnel plots and a regression analysis. Overall, 31 studies were retrieved, and of them, 17 reported on the point prevalence of respiratory pathogens, with pooled estimates of 4.91 cases per 1000 HP (95%CI: 2.46 to 9.80) for RSV, 3.47 per 1000 HP for influenza and 40.21 cases per 1000 HP (95%CI: 14.66 to 105.55) for SARS-CoV-2. Incidence estimates were calculated from 12 studies, and SARS-CoV-2 was characterized by the highest occurrence (9.58 diagnoses per 1000 persons-months, 95%CI: 3.00 to 16.16), followed by influenza (6.07, 95%CI: 0.00 to 15.06) and RSV (1.71, 95%CI: 0.00 to 4.13). Only four studies reported on the outcome of viral infections in HP: the assessed pathogens were associated with a high likelihood of hospitalization, while high rates of recurrence and eventual deaths were reported in cases of RSV infections. In summary, RSV, influenza and SARS-CoV-2 infections were documented in HP from urban shelters, and their potential outcomes stress the importance of specifically tailored preventive strategies.

Clinical features and outcomes of influenza and RSV coinfections: a report from Canadian immunization research network serious outcomes surveillance network

BACKGROUND

Influenza and RSV coinfections are not commonly seen but are concerning as they can lead to serious illness and adverse clinical outcomes among vulnerable populations. Here we describe the clinical features and outcomes of influenza and RSV coinfections in hospitalized adults.

METHODS

A cohort study was performed with pooled active surveillance in hospitalized adults ≥ 50 years from the Serious Outcomes Surveillance Network of the Canadian Immunization Research Network (CIRN SOS) during the 2012/13, 2013/14, and 2014/15 influenza seasons. Descriptive statistics summarized the characteristics of influenza/RSV coinfections. Kaplan-Meier estimated the probability of survival over the first 30 days of hospitalization.

RESULTS

Over three influenza seasons, we identified 33 cases of RSV and influenza coinfection, accounting for 2.39 cases per 1,000 hospitalizations of patients with acute respiratory illnesses. Adults aged 50 + years commonly reported cough (81.8%), shortness of breath (66.7%), sputum production (45.5%), weakness (33.3%), fever (27.3%), and nasal congestion (24.2%) as constitutional and lower respiratory tract infection symptoms. The mortality rate was substantial (12.1%), and age, comorbidity burden, and frailty were associated with a higher risk for adverse clinical outcomes.

CONCLUSIONS

Older adults are at higher risk for complications from influenza and RSV coinfections, especially those over 65 with a high comorbidity burden and frailty.

All Eyes on the Prefusion-Stabilized F Construct, but Are We Missing the Potential of Alternative Targets for Respiratory Syncytial Virus Vaccine Design?

Respiratory Syncytial Virus (RSV) poses a significant global health concern as a major cause of lower respiratory tract infections (LRTIs). Over the last few years, substantial efforts have been directed towards developing vaccines and therapeutics to combat RSV, leading to a diverse landscape of vaccine candidates. Notably, two vaccines targeting the elderly and the first maternal vaccine have recently been approved. The majority of the vaccines and vaccine candidates rely solely on a prefusion-stabilized conformation known for its highly neutralizing epitopes. Although, so far, this antigen design appears to be successful for the elderly, our current understanding remains incomplete, requiring further improvement and refinement in this field. Pediatric vaccines still have a long journey ahead, and we must ensure that vaccines currently entering the market do not lose efficacy due to the emergence of mutations in RSV's circulating strains. This review will provide an overview of the current status of vaccine designs and what to focus on in the future. Further research into antigen design is essential, including the exploration of the potential of alternative RSV proteins to address these challenges and pave the way for the development of novel and effective vaccines, especially in the pediatric population.

Current state and challenges in respiratory syncytial virus drug discovery and development

Human respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections (LRTI) in young children and elderly people worldwide. Recent significant progress in our understanding of the structure and function of RSV proteins has led to the discovery of several clinical candidates targeting RSV fusion and replication. These include both the development of novel small molecule interventions and the isolation of potent monoclonal antibodies. In this review, we summarize the state-of-the-art of RSV drug discovery, with a focus on the characteristics of the candidates that reached the clinical stage of development. We also discuss the lessons learned from failed and discontinued clinical developments and highlight the challenges that remain for development of RSV therapies.

Controlled Human Infection Challenge Studies with RSV

Despite considerable momentum in the development of RSV vaccines and therapeutics, there remain substantial barriers to the development and licensing of effective agents, particularly in high-risk populations. The unique immunobiology of RSV and lack of clear protective immunological correlates has held back RSV vaccine development, which, therefore, depends on large and costly clinical trials to demonstrate efficacy. Studies involving the deliberate infection of human volunteers offer an intermediate step between pre-clinical and large-scale studies of natural infection. Human challenge has been used to demonstrate the potential efficacy of vaccines and antivirals while improving our understanding of the protective immunity against RSV infection. Early RSV human infection challenge studies determined the role of routes of administration and size of inoculum on the disease. However, inherent limitations, the use of highly attenuated/laboratory-adapted RSV strains and the continued evolutionary adaptation of RSV limits extrapolation of results to present-day vaccine testing. With advances in technology, it is now possible to perform more detailed investigations of human mucosal immunity against RSV in experimentally infected adults and, more recently, older adults to optimise the design of vaccines and novel therapies. These studies identified defects in RSV-induced humoral and CD8+ T cell immunity that may partly explain susceptibility to recurrent RSV infection. We discuss the insights from human infection challenge models, ethical and logistical considerations, potential benefits, and role in streamlining and accelerating novel antivirals and vaccines against RSV. Finally, we consider how human challenges might be extended to include relevant at-risk populations.

Efficacy and Safety of an mRNA-Based RSV PreF Vaccine in Older Adults

BACKGROUND

Respiratory syncytial virus (RSV) can cause substantial morbidity and mortality among older adults. An mRNA-based RSV vaccine, mRNA-1345, encoding the stabilized RSV prefusion F glycoprotein, is under clinical investigation.

METHODS

In this ongoing, randomized, double-blind, placebo-controlled, phase 2-3 trial, we randomly assigned, in a 1:1 ratio, adults 60 years of age or older to receive one dose of mRNA-1345 (50 μg) or placebo. The two primary efficacy end points were the prevention of RSV-associated lower respiratory tract disease with at least two signs or symptoms and with at least three signs or symptoms. A key secondary efficacy end point was the prevention of RSV-associated acute respiratory disease. Safety was also assessed.

RESULTS

Overall, 35,541 participants were assigned to receive the mRNA-1345 vaccine (17,793 participants) or placebo (17,748). The median follow-up was 112 days (range, 1 to 379). The primary analyses were conducted when at least 50% of the anticipated cases of RSV-associated lower respiratory tract disease had occurred. Vaccine efficacy was 83.7% (95.88% confidence interval [CI], 66.0 to 92.2) against RSV-associated lower respiratory tract disease with at least two signs or symptoms and 82.4% (96.36% CI, 34.8 to 95.3) against the disease with at least three signs or symptoms. Vaccine efficacy was 68.4% (95% CI, 50.9 to 79.7) against RSV-associated acute respiratory disease. Protection was observed against both RSV subtypes (A and B) and was generally consistent across subgroups defined according to age and coexisting conditions. Participants in the mRNA-1345 group had a higher incidence than those in the placebo group of solicited local adverse reactions (58.7% vs. 16.2%) and of systemic adverse reactions (47.7% vs. 32.9%); most reactions were mild to moderate in severity and were transient. Serious adverse events occurred in 2.8% of the participants in each trial group.

CONCLUSIONS

A single dose of the mRNA-1345 vaccine resulted in no evident safety concerns and led to a lower incidence of RSV-associated lower respiratory tract disease and of RSV-associated acute respiratory disease than placebo among adults 60 years of age or older. (Funded by Moderna; ConquerRSV ClinicalTrials.gov number, NCT05127434.).

Respiratory syncytial virus in adults with comorbidities: an update on epidemiology, vaccines, and treatments

BACKGROUND

Respiratory syncytial virus (RSV) is widely known as a frequent cause of respiratory distress among adults, particularly in older people. Recent years have witnessed several improvements in respiratory virus detection, leading to more questions about therapeutic management strategies.

OBJECTIVES

This narrative review focuses on the RSV burden in older people and adults with risk factors and provides an update on the main recent developments regarding managing this infection.

SOURCES

A comprehensive PubMed search was conducted till August 2023 to identify studies on RSV among the adult population. We included observational studies, RCTs on vaccines, and different therapies.

CONTENT

This review should give clinicians an overview of RSV epidemiology and burden among older people and adults with pre-existing risk factors, the most recent randomized clinical trials on RSV vaccines, and the existing data on the different therapeutics existing and under development.

IMPLICATIONS

There is a growing body of evidence on RSV burden in adults. The landscape of preventive and curative treatments is quickly evolving.

Estimation of the Number of Respiratory Syncytial Virus-Associated Hospitalizations in Adults in the European Union

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infections in adults that can result in hospitalizations. Estimating RSV-associated hospitalization is critical for planning RSV-related healthcare across Europe.

METHODS

We gathered RSV-associated hospitalization estimates from the RSV Consortium in Europe (RESCEU) for adults in Denmark, England, Finland, Norway, Netherlands, and Scotland from 2006 to 2017. We extrapolated these estimates to 28 European Union (EU) countries using nearest-neighbor matching, multiple imputations, and 2 sets of 10 indicators.

RESULTS

On average, 158 229 (95% confidence interval [CI], 140 865-175 592) RSV-associated hospitalizations occur annually among adults in the EU (≥18 years); 92% of these hospitalizations occur in adults ≥65 years. Among 75-84 years, the annual average is estimated at 74 519 (95% CI, 69 923-79 115) at a rate of 2.24 (95% CI, 2.10-2.38) per 1000. Among ≥85 years, the annual average is estimated at 37 904 (95% CI, 32 444-43 363) at a rate of 2.99 (95% CI, 2.56-3.42).

CONCLUSIONS

Our estimates of RSV-associated hospitalizations in adults are the first analysis integrating available data to provide the disease burden across the EU. Importantly, for a condition considered in the past to be primarily a disease of young children, the average annual hospitalization estimate in adults was lower but of a similar magnitude to the estimate in young children (0-4 years): 158 229 (95% CI, 140 865-175 592) versus 245 244 (95% CI, 224 688-265 799).

Respiratory syncytial virus infection and novel interventions

The large global burden of respiratory syncytial virus (RSV) respiratory tract infections in young children and older adults has gained increased recognition in recent years. Recent discoveries regarding the neutralization-specific viral epitopes of the pre-fusion RSV glycoprotein have led to a shift from empirical to structure-based design of RSV therapeutics, and controlled human infection model studies have provided early-stage proof of concept for novel RSV monoclonal antibodies, vaccines and antiviral drugs. The world's first vaccines and first monoclonal antibody to prevent RSV among older adults and all infants, respectively, have recently been approved. Large-scale introduction of RSV prophylactics emphasizes the need for active surveillance to understand the global impact of these interventions over time and to timely identify viral mutants that are able to escape novel prophylactics. In this Review, we provide an overview of RSV interventions in clinical development, highlighting global disease burden, seasonality, pathogenesis, and host and viral factors related to RSV immunity.

Respiratory Syncytial Virus Prefusion F Subunit Vaccine: First Approval of a Maternal Vaccine to Protect Infants

Pfizer is developing a bivalent respiratory syncytial virus (RSV) prefusion F subunit vaccine (RSVpreF; ABRYSVO™) for preventing RSV illness in infants and individuals aged ≥ 60 years. RSVpreF received approval for vaccination of pregnant individuals to help protect infants against RSV illness on 21 August 2023 in the USA. RSVpreF is also approved in the USA (31 May 2023) for active immunization of individuals aged ≥ 60 years for the prevention of lower respiratory tract disease (LRTD) caused by RSV. In the EU, RSVpreF has received approval for both indications, and it has been submitted for regulatory approval in Canada (both indications) and in Japan (maternal immunization to protect infants). This article summarizes the milestones in the development of RSVpreF leading to the approval for use in pregnant individuals to prevent LRTD in infants.

T cells, more than antibodies, may prevent symptoms developing from respiratory syncytial virus infections in older adults

Introduction

The immune mechanisms supporting partial protection from reinfection and disease by the respiratory syncytial virus (RSV) have not been fully characterized. In older adults, symptoms are typically mild but can be serious in patients with comorbidities when the infection extends to the lower respiratory tract.

Methods

This study formed part of the RESCEU older-adults prospective-cohort study in Northern Europe (2017-2019; NCT03621930) in which a thousand participants were followed over an RSV season. Peripheral-blood samples (taken pre-season, post-season, during illness and convalescence) were analyzed from participants who (i) had a symptomatic acute respiratory tract infection by RSV (RSV-ARTI; N=35) or (ii) asymptomatic RSV infection (RSV-Asymptomatic; N=16). These analyses included evaluations of antibody (Fc-mediated-) functional features and cell-mediated immunity, in which univariate and machine-learning (ML) models were used to explore differences between groups.

Results

Pre-RSV-season peripheral-blood biomarkers were predictive of symptomatic RSV infection. T-cell data were more predictive than functional antibody data (area under receiver operating characteristic curve [AUROC] for the models were 99% and 76%, respectively). The pre-RSV season T-cell phenotypes which were selected by the ML modelling and which were more frequent in RSV-Asymptomatic group than in the RSV-ARTI group, coincided with prominent phenotypes identified during convalescence from RSV-ARTI (e.g., IFN-γ+, TNF-α+ and CD40L+ for CD4+, and IFN-γ+ and 4-1BB+ for CD8+).

Conclusion

The evaluation and statistical modelling of numerous immunological parameters over the RSV season suggests a primary role of cellular immunity in preventing symptomatic RSV infections in older adults.

Underascertainment of Respiratory Syncytial Virus Infection in Adults Due to Diagnostic Testing Limitations: A Systematic Literature Review and Meta-analysis

BACKGROUND

Most observational population-based studies identify respiratory syncytial virus (RSV) by nasal/nasopharyngeal swab reverse transcriptase real-time PCR (RT-PCR) only. We conducted a systematic review and meta-analyses to quantify specimen and diagnostic testing-based underascertainment of adult RSV infection.

METHODS

EMBASE, PubMed, and Web of Science were searched (January 2000-December 2021) for studies including adults using/comparing >1 RSV testing approach. We quantified test performance and RSV detection increase associated with using multiple specimen types.

RESULTS

Among 8066 references identified, 154 met inclusion. Compared to RT-PCR, other methods were less sensitive: rapid antigen detection test (RADT; pooled sensitivity, 64%), direct fluorescent antibody (DFA; 83%), and viral culture (86%). Compared to singleplex PCR, multiplex PCR's sensitivity was lower (93%). Compared to nasal/nasopharyngeal swab RT-PCR alone, adding another specimen type increased detection: sputum RT-PCR, 52%; 4-fold rise in paired serology, 44%; and oropharyngeal swab RT-PCR, 28%. Sensitivity was lower in estimates limited to only adults (for RADT, DFA, and viral culture), and detection rate increases were largely comparable.

CONCLUSIONS

RT-PCR, particularly singleplex testing, is the most sensitive RSV diagnostic test in adults. Adding additional specimen types to nasopharyngeal swab RT-PCR testing increased RSV detection. Synergistic effects of using ≥3 specimen types should be assessed, as this approach may improve the accuracy of adult RSV burden estimates.

Cost-effectiveness of the adjuvanted quadrivalent influenza vaccine in the elderly Belgian population

BACKGROUND

Between 2015 and 2019, when 62% of Belgian adults aged ≥ 65 years were vaccinated with standard quadrivalent influenza vaccines, influenza caused an average of 3,905 hospitalizations and 347 premature deaths per year in older adults. The objective of the present analysis was to estimate the cost-effectiveness of the adjuvanted quadrivalent influenza vaccine (aQIV) compared to the standard (SD-QIV) and high-dose (HD-QIV) vaccines in elderly Belgians.

RESEARCH DESIGN AND METHODS

The analysis was based on a static cost-effectiveness model that captured the evolution of patients infected with influenza and was customized with available national data.

RESULTS

Vaccinating adults aged ≥ 65 years with aQIV instead of SD-QIV would decrease the number of hospitalizations by 530 and the number of deaths by 66 in the 2023-2024 influenza season. aQIV was cost-effective compared to SD-QIV with an incremental cost of €15,227/quality-adjusted life year (QALY). aQIV is cost-saving when compared to HD-QIV in the subgroup of institutionalized elderly adults who were granted reimbursement for this vaccine.

CONCLUSION

In a health care system striving to improve the prevention of infectious diseases, a cost-effective vaccine such as aQIV is a key asset to reduce the number of influenza-related hospitalizations and premature deaths in older adults.

PLAIN LANGUAGE SUMMARY

A flu vaccine containing a unique immune boosting additive reduces medical spending by reducing flu hospitalizations and early deaths in the elderly.

Predicted Public Health and Economic Impact of Respiratory Syncytial Virus Vaccination with Variable Duration of Protection for Adults ≥60 Years in Belgium

Respiratory syncytial virus (RSV) is a leading cause of acute respiratory infection (ARI) in older adults. This study used a static, cohort-based decision-tree model to estimate the public health and economic impact of vaccination against RSV in Belgians aged ≥60 years compared with no vaccination for different vaccine duration of protection profiles from a healthcare payer perspective. Three vaccine protection durations were compared (1, 3, and 5 years), and several sensitivity and scenario analyses were performed. Results showed that an RSV vaccine with a 3-year duration of protection would prevent 154,728 symptomatic RSV-ARI cases, 3688 hospitalizations, and 502 deaths over three years compared to no vaccination in older adults and would save EUR 35,982,857 in direct medical costs in Belgium. The number needed to vaccinate to prevent one RSV-ARI case was 11 for the 3-year duration profile, while it was 28 and 8 for the 1- and 5-year vaccine duration profiles, respectively. The model was generally robust in sensitivity analyses varying key input values. This study suggested that vaccination could substantially decrease the public health and economic burden of RSV in adults ≥60 years in Belgium, with benefits increasing with a longer duration of vaccine protection.