Influenza- and respiratory syncytial virus-associated mortality and hospitalisations

How Does the Burden of Respiratory Syncytial Virus Compare to Influenza in Spanish Adults?

BACKGROUND

Respiratory syncytial virus (RSV) and influenza infections cause significant annual morbidity and mortality worldwide in at-risk populations. This study is aimed at assessing hospital burden and healthcare resource utilization (HRU) of RSV and influenza in adults in Spain.

METHODS

Data were obtained from the Projected Hospitalisation Database of inpatient episodes (ages: younger adults 18-50 and 51-64 years; older adults 65-74, 75-84, and ≥ 85 years) during 2015, 2017, and 2018 in Spanish public hospitals. Incidence, mean hospitalization, and HRU assessments, including length of stay (LOS), intensive care unit (ICU) usage, and age-standardized mortality rates, were collected and stratified by age group, with analyses focusing on the adult population (≥ 18 years old).

RESULTS

Mean hospitalization rate in the population across all years was lower in individuals with RSV versus influenza (7.2/100,000 vs. 49.7/100,000 individuals). ICU admissions and median LOS were similar by age group for both viruses. Age-standardized mortality was 6.3/100,000 individuals and 6.1/100,000 individuals in patients with RSV and influenza, respectively, and mortality rates were similar in older adults (≥ 65 years) for both viruses.

CONCLUSIONS

RSV and influenza infection were associated with considerable HRU. There is a substantial disease burden for RSV infection in older adults ≥ 65 years. While RSV hospitalization rates in adults reported here appeared lower than influenza, RSV is still underdiagnosed in the hospital setting and its incidence might be similar to, or higher than, influenza.

Estimated Incidence of Hospitalizations and Deaths Attributable to Respiratory Syncytial Virus Infections Among Adults in Germany Between 2015 and 2019

INTRODUCTION

Respiratory syncytial virus (RSV) burden in adults is underestimated mainly due to unspecific symptoms and limited standard-of-care testing. We estimated the population-based incidence of hospitalization and mortality attributable to RSV among adults with and without risk factors in Germany.

METHODS

Weekly counts of hospitalizations and deaths for respiratory, cardiovascular, and cardiorespiratory diseases were obtained (Statutory Health Insurance database, 2015-2019). A quasi-Poisson regression model was fitted to estimate the number of hospitalizations and deaths attributable to RSV as a function of periodic and aperiodic time trends, and viral activity while allowing for potential overdispersion. Weekly counts of RSV and influenza hospitalizations in children < 2 years and adults ≥ 60 years, respectively, were used as viral activity indicators. Models were stratified by age group and risk status (defined as presence of selected comorbidities).

RESULTS

Population-based RSV-attributable hospitalization incidence rates were high among adults ≥ 60 years: respiratory hospitalizations (236-363 per 100,000 person-years) and cardiorespiratory hospitalizations (584-912 per 100,000 person-years). RSV accounted for 2-3% of all cardiorespiratory hospitalizations in this age group. The increase in cardiorespiratory hospitalization risk associated with underlying risk factors was greater in 18-44 year old persons (five to sixfold higher) than in ≥ 75 year old persons (two to threefold higher).

CONCLUSIONS

This is a first model-based study to comprehensively assess adult RSV burden in Germany. Estimated cardiorespiratory RSV hospitalization rates increased with age and were substantially higher in people with risk factors compared to those without risk factors. Our study indicates that RSV, like other respiratory viruses, contributes to both respiratory and cardiovascular hospitalizations. Effective prevention strategies are needed, especially among older adults ≥ 60 years and among adults with underlying risk factors.

Life-threatening infections in human newborns: Reconciling age-specific vulnerability and interindividual variability

In humans, the interindividual variability of clinical outcome following exposure to a microorganism is immense, ranging from silent infection to life-threatening disease. Age-specific immune responses partially account for the high incidence of infection during the first 28 days of life and the related high mortality at population level. However, the occurrence of life-threatening disease in individual newborns remains unexplained. By contrast, inborn errors of immunity and their immune phenocopies are increasingly being discovered in children and adults with life-threatening viral, bacterial, mycobacterial and fungal infections. There is a need for convergence between the fields of neonatal immunology, with its in-depth population-wide characterization of newborn-specific immune responses, and clinical immunology, with its investigations of infections in patients at the cellular and molecular levels, to facilitate identification of the mechanisms of susceptibility to infection in individual newborns and the design of novel preventive and therapeutic strategies.

Potential co-infection of influenza A, influenza B, respiratory syncytial virus, and Chlamydia pneumoniae: a case report with literature review

The occurrence of a co-infection involving four distinct respiratory pathogens could be underestimated. Here, we report the case of a 72-year-old woman who presented to a community hospital with a cough productive of sputum as her main clinical manifestation. Antibody detection of common respiratory pathogens revealed potential co-infection with influenza A, influenza B, respiratory syncytial virus, and Chlamydia pneumoniae. We treated her with 75 mg oseltamivir phosphate administered orally twice daily for 5 days, 0.5 g azithromycin administered orally for 5 days, and 0.3 g acetylcysteine aerosol inhaled twice daily for 3 days. The patient showed a favorable outcome on the eighth day after early diagnosis and treatment. Since co-infection with these four pathogens is rare, we performed an extensive PubMed search of similar cases and carried out a systematic review to analyze the epidemiology, clinical manifestations, transmission route, susceptible population, and outcomes of these four different pathogens. Our report highlights the importance for general practitioners to be vigilant about the possibility of mixed infections when a patient presents with respiratory symptoms. Although these symptoms may be mild, early diagnosis and timely treatment could improve outcomes. Additionally, further research is warranted to explore the potential influence of SARS-CoV-2 infection on the co-occurrence of multiple respiratory pathogens.

Vaccine induced memory CD8+ T cells efficiently prevent viral transmission from the respiratory tract

Introduction

Mucosal immunization eliciting local T-cell memory has been suggested for improved protection against respiratory infections caused by viral variants evading pre-existing antibodies. However, it remains unclear whether T-cell targeted vaccines suffice for prevention of viral transmission and to which extent local immunity is important in this context.

Methods

To study the impact of T-cell vaccination on the course of viral respiratory infection and in particular the capacity to inhibit viral transmission, we used a mouse model involving natural murine parainfluenza infection with a luciferase encoding virus and an adenovirus based nucleoprotein targeting vaccine.

Results and discussion

Prior intranasal immunization inducing strong mucosal CD8+ T cell immunity provided an almost immediate shut-down of the incipient infection and completely inhibited contact based viral spreading. If this first line of defense did not operate, as in parentally immunized mice, recirculating T cells participated in accelerated viral control that reduced the intensity of inter-individual transmission. These observations underscore the importance of pursuing the development of mucosal T-cell inducing vaccines for optimal protection of the individual and inhibition of inter-individual transmission (herd immunity), while at the same time explain why induction of a strong systemic T-cell response may still impact viral transmission.

Fading SARS-CoV-2 humoral VOC cross-reactivity and sustained cellular immunity in convalescent children and adolescents

Cross-reactive cellular and humoral immunity can substantially contribute to antiviral defense against SARS-CoV-2 variants of concern (VOC). While the adult SARS-CoV-2 cellular and humoral immunity and its cross-recognition potential against VOC is broadly analyzed, similar data regarding the pediatric population are missing. In this study, we perform an analysis of the humoral and cellular SARS-CoV-2 response immune of 32 convalescent COVID-19 children (children), 27 convalescent vaccinated adults(C + V+) and 7 unvaccinated convalescent adults (C + V-). Similarly to adults, a significant reduction of cross-reactive neutralizing capacity against delta and omicron VOC was observed 6 months after SARS-CoV-2 infection. While SAR-CoV-2 neutralizing capacity was comparable among children and C + V- against all VOC, children demonstrated as expected an inferior humoral response when compared to C + V+. Nevertheless, children generated SARS-CoV-2 reactive T cells with broad cross-recognition potential. When compared to V + C+, children presented even comparable frequencies of WT-reactive CD4 + and CD8 + T cells with high avidity and functionality. Taking into consideration the limitations of study - unknown disease onset for 53% of the asymptomatic pediatric subjects, serological detection of SARS-CoV-2 infection-, our results suggest that following SARS-CoV-2 infection children generate a humoral SARS-CoV-2 response with neutralizing potential comparable to unvaccinated COVID-19 convalescent adults as well a sustained SARS-CoV-2 cellular response cross-reactive to VOC.

Understanding the age spectrum of respiratory syncytial virus associated hospitalisation and mortality burden based on statistical modelling methods: a systematic analysis

BACKGROUND

Statistical modelling studies based on excess morbidity and mortality are important for understanding RSV disease burden for age groups that are less frequently tested for RSV. We aimed to understand the full age spectrum of RSV morbidity and mortality burden based on statistical modelling studies, as well as the value of modelling studies in RSV disease burden estimation.

METHODS

The databases Medline, Embase and Global Health were searched to identify studies published between January 1, 1995, and December 31, 2021, reporting RSV-associated excess hospitalisation or mortality rates of any case definitions using a modelling approach. All reported rates were summarised using median, IQR (Interquartile range) and range by age group, outcome and country income group; where applicable, a random-effects meta-analysis was conducted to combine the reported rates. We further estimated the proportion of RSV hospitalisations that could be captured in clinical databases.

RESULTS

A total of 32 studies were included, with 26 studies from high-income countries. RSV-associated hospitalisation and mortality rates both showed a U-shape age pattern. Lowest and highest RSV acute respiratory infection (ARI) hospitalisation rates were found in 5-17 years (median: 1.6/100,000 population, IQR: 1.3-18.5) and < 1 year (2235.7/100,000 population, 1779.1-3552.5), respectively. Lowest and highest RSV mortality rates were found in 18-49 years (0.1/100,000 population, 0.06-0.2) and ≥ 75 years (80.0/100,000 population, 70.0-90.0) for high-income countries, respectively, and in 18-49 years (0.3/100,000 population, 0.1-2.4) and < 1 year (143.4/100,000 population, 143.4-143.4) for upper-middle income countries. More than 70% of RSV hospitalisations in children < 5 years could be captured in clinical databases whereas less than 10% of RSV hospitalisations could be captured in adults, especially for adults ≥ 50 years. Using pneumonia and influenza (P&I) mortality could potentially capture half of all RSV mortality in older adults but only 10-30% of RSV mortality in children.

CONCLUSIONS

Our study provides insights into the age spectrum of RSV hospitalisation and mortality. RSV disease burden using laboratory records alone could be substantially severely underreported for age groups ≥ 5 years. Our findings confirm infants and older adults should be prioritised for RSV immunisation programmes.

TRIAL REGISTRATION

PROSPERO CRD42020173430.

Development of Respiratory Syncytial Virus Vaccine Candidates for the Elderly

Respiratory syncytial virus (RSV) is a significant threat to elderly populations and repeated infections that occur throughout life are poorly protective. To assess the role of prior RSV infections as well as elderly immune senescence on vaccine efficacy, we compared immune responses after virus-like particle (VLP) immunization of elderly cotton rats and young cotton rats, both previously RSV infected, in order to mimic the human population. We show that immunization of RSV-experienced young or elderly animals resulted in the same levels of anti-pre-F IgG, anti-G IgG, neutralizing antibody titers, and protection from challenge indicating that the delivery of F and G proteins in a VLP is equally effective in activation of protective responses in both elderly and young populations. Our results suggest that F and G protein-containing VLPs induce anti-RSV memory established in prior RSV infections equally well in both young and elderly animals and thus can be an effective vaccine for 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.

Economic burden of respiratory syncytial virus infection in adults: a systematic literature review

AIMS

Capture the economic and healthcare resource utilization (HCRU) burden in older adults due to respiratory syncytial virus (RSV) infection.

METHODS

An electronic literature search of PubMed, Embase, the Cochrane Library, PsycINFO, and EconLit was conducted for studies of the cost and HCRU outcomes of RSV infection in adult patients, with no language or country restrictions. Search dates for primary studies were January 1, 2002-May 18, 2022. The methodological quality of included studies was assessed using a modification of the Critical Appraisal Skills Programme (CASP) checklist for economic studies and the Drummond checklist.

RESULTS

42 studies were identified that reported cost or HCRU data associated with RSV infections, with geographic locations across North America, South America, Europe, Asia, and Oceania. Generally, hospitalization costs were highest in the United States (US). Driving factors of increased cost included older age, comorbidities, and length of stay. US studies found that the national direct cost burden of RSV hospitalizations was $1.3 billion for all adults and $1.5-$4.0 billion for adults aged ≥60 years (estimates for other countries were not identified). Studies estimating incremental costs for RSV cases versus controls and costs pre- and post-RSV infection demonstrated higher costs for RSV cases. Hospitalizations accounted for the majority of total costs.

Focusing on severe infections with the respiratory syncytial virus (RSV) in adults: Risk factors, symptomatology and clinical course compared to influenza A / B and the original SARS-CoV-2 strain

BACKGROUND

The role and impact of RSV in the adult population is not well understood and comparative data of RSV infection, influenza A/B and SARS-CoV-2 in the elderly hospitalized for respiratory infections is limited.

METHODS

In a retrospective, monocentric study we analyzed data of adult patients with respiratory infections tested positive by PCR for RSV, Influenza A/B and SARS-CoV-2 over a four-year period from 2017 to 2020. Symptoms on admission, laboratory results, and risk factors were assessed, and the clinical course and outcomes were studied.

RESULTS

A total of 1541 patients hospitalized with respiratory disease and PCR positive for one of the 4 viruses were enrolled in the study. RSV was the second most prevalent virus before the COVID-19 pandemic and RSV patients represent the oldest group in this study with an average age of 75 years. Neither clinical nor laboratory characteristics differ clearly between RSV, Influenza A / B and SARS-CoV-2 infections. Up to 85% of patients had risk factors, with COPD and kidney disease found particularly frequently in RSV infections. Hospital stay was 12.66 days for RSV patients and thus significantly longer than for influenza A / B (10.88 and 8.86, respectively, p < 0.001), but shorter than for SARS-CoV-2 (17.87 days, p < 0.001). The risk for ICU admission and the rate of mechanical ventilation were also higher for RSV than for influenza A (OR 1.69 (p = 0.020) and 1.59 (p = 0.050)) and influenza B: (1.98 (p = 0.018) and 2.33 (p < 0.001)), but lower than for SARS-CoV-2 (0.65 (p < 0.001) and 0.59 (p = 0.035)). The risk of hospital mortality for RSV was increased compared with influenza A (1.55 (p = 0.050)) and influenza B (1.42 (p = 0.262)), but lower compared to SARs-CoV-2 (0.37 (p < 0.001).

CONCLUSION

RSV infections in elderly are frequent and more severe than those with influenza A/B. While the impact of SARS-CoV-2 most likely decreased in the elderly population due to vaccination, RSV can be expected to continue to be problematic for elderly patients, especially those with comorbidities and thus, more awareness on the disastrous impact of RSV in this age group is urgently needed.

Direct RNA sequencing of respiratory syncytial virus infected human cells generates a detailed overview of RSV polycistronic mRNA and transcript abundance

To characterize species of viral mRNA transcripts generated during respiratory syncytial virus (RSV) infection, human fibroblast-like MRC-5 lung cells were infected with subgroup A RSV for 6, 16 and 24 hours. In addition, we characterised the viral transcriptome in infected Calu-3 lung epithelial cells at 48 hours post infection. Total RNA was harvested and polyadenylated mRNA was enriched and sequenced by direct RNA sequencing using an Oxford nanopore device. This platform yielded over 450,000 direct mRNA transcript reads which were mapped to the viral genome and analysed to determine the relative mRNA levels of viral genes using our in-house ORF-centric pipeline. We examined the frequency of polycistronic readthrough mRNAs were generated and assessed the length of the polyadenylated tails for each group of transcripts. We show a general but non-linear decline in gene transcript abundance across the viral genome, as predicted by the model of RSV gene transcription. However, the decline in transcript abundance is not uniform. The polyadenylate tails generated by the viral polymerase are similar in length to those generated by the host polyadenylation machinery and broadly declined in length for most transcripts as the infection progressed. Finally, we observed that the steady state abundance of transcripts with very short polyadenylate tails less than 20 nucleotides is less for N, SH and G transcripts in both cell lines compared to NS1, NS2, P, M, F and M2 which may reflect differences in mRNA stability and/or translation rates within and between the cell lines.

SARS-CoV-2-specific T cell memory with common TCRαβ motifs is established in unvaccinated children who seroconvert after infection

As the establishment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell memory in children remains largely unexplored, we recruited convalescent COVID-19 children and adults to define their circulating memory SARS-CoV-2-specific CD4+ and CD8+ T cells prior to vaccination. We analyzed epitope-specific T cells directly ex vivo using seven HLA class I and class II tetramers presenting SARS-CoV-2 epitopes, together with Spike-specific B cells. Unvaccinated children who seroconverted had comparable Spike-specific but lower ORF1a- and N-specific memory T cell responses compared with adults. This agreed with our TCR sequencing data showing reduced clonal expansion in children. A strong stem cell memory phenotype and common T cell receptor motifs were detected within tetramer-specific T cells in seroconverted children. Conversely, children who did not seroconvert had tetramer-specific T cells of predominantly naive phenotypes and diverse TCRαβ repertoires. Our study demonstrates the generation of SARS-CoV-2-specific T cell memory with common TCRαβ motifs in unvaccinated seroconverted children after their first virus encounter.

Modelled estimates of hospitalisations attributable to respiratory syncytial virus and influenza in Australia, 2009-2017

Background

Respiratory syncytial virus (RSV) and influenza are important causes of disease in children and adults. In Australia, information on the burden of RSV in adults is particularly limited.

Methods

We used time series analysis to estimate respiratory, acute respiratory infection, pneumonia and influenza, and bronchiolitis hospitalisations attributable to RSV and influenza in Australia during 2009 through 2017. RSV and influenza‐coded hospitalisations in <5‐year‐olds were used as proxies for relative weekly viral activity.

Results

From 2009 to 2017, the estimated all‐age average annual rates of respiratory hospitalisations attributable to RSV and seasonal influenza (excluding 2009) were 54.8 (95% confidence interval [CI]: 20.1, 88.8) and 87.8 (95% CI: 74.5, 97.7) per 100,000, respectively. The highest estimated average annual RSV‐attributable respiratory hospitalisation rate per 100,000 was 464.2 (95% CI: 285.9, 641.2) in <5‐year‐olds. For seasonal influenza, it was 521.6 (95% CI: 420.9, 600.0) in persons aged ≥75 years. In ≥75‐year‐olds, modelled estimates were approximately eight and two times the coded estimates for RSV and seasonal influenza, respectively.

Conclusions

RSV and influenza are major causes of hospitalisation in young children and older adults in Australia, with morbidity underestimated by hospital diagnosis codes.

Evaluation of the influenza and respiratory syncytial virus (RSV) targets in the AusDiagnostics SARS-CoV-2, Influenza and RSV 8-well assay: sample pooling increases testing throughput

During the COVID-19 pandemic, sample pooling has proven an effective strategy to overcome the limitations of reagent shortages and expand laboratory testing capacity. The inclusion of influenza and respiratory syncytial virus (RSV) in a multiplex tandem PCR platform with SARS-CoV-2 provides useful diagnostic and infection control information. This study aimed to evaluate the performance of the influenza and RSV targets in the AusDiagnostics SARS-CoV-2, Influenza and RSV 8-well assay, including the effect of pooling samples on target detection. RSV target detection in clinical samples was compared to the Cepheid Xpert Xpress Flu/RSV assay as a reference standard. Samples were then tested in pools of four and detection rates were compared. Owing to the unavailability of clinical samples for influenza, only the effect of sample pooling on simulated samples was evaluated for these targets. RSV was detected in neat clinical samples with a positive percent agreement (PPA) of 100% and negative percent agreement (NPA) of 99.5% compared to the reference standard, demonstrating 99.7% agreement. This study demonstrates that sample pooling by four increases the average Ct value by 2.24, 2.29, 2.20 and 1.91 cycles for the target's influenza A, influenza A typing, influenza B and RSV, respectively. The commercial AusDiagnostics SARS-CoV-2, Influenza and RSV 8-well assay was able to detect influenza and RSV at an intermediate concentration within the limit of detection of the assay. Further studies to explore the applicability of sample pooling at the lower limit of detection of the assay is needed. Nevertheless, sample pooling has shown to be a viable strategy to increase testing throughput and reduce reagent usage. In addition, the multiplexed platform targeting various respiratory viruses assists with public health and infection control responses, clinical care, and patient management.

Predictors of all-cause mortality among patients hospitalized with influenza, respiratory syncytial virus, or SARS-CoV-2

Background

Shared and divergent predictors of clinical severity across respiratory viruses may support clinical and community responses in the context of a novel respiratory pathogen.

Methods

We conducted a retrospective cohort study to identify predictors of 30‐day all‐cause mortality following hospitalization with influenza (N = 45,749; 2010‐09 to 2019‐05), respiratory syncytial virus (RSV; N = 24 345; 2010‐09 to 2019‐04), or severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2; N = 8988; 2020‐03 to 2020‐12; pre‐vaccine) using population‐based health administrative data from Ontario, Canada. Multivariable modified Poisson regression was used to assess associations between potential predictors and mortality. We compared the direction, magnitude, and confidence intervals of risk ratios to identify shared and divergent predictors of mortality.

Results

A total of 3186 (7.0%), 697 (2.9%), and 1880 (20.9%) patients died within 30 days of hospital admission with influenza, RSV, and SARS‐CoV‐2, respectively. Shared predictors of increased mortality included older age, male sex, residence in a long‐term care home, and chronic kidney disease. Positive associations between age and mortality were largest for patients with SARS‐CoV‐2. Few comorbidities were associated with mortality among patients with SARS‐CoV‐2 as compared with those with influenza or RSV.

Conclusions

Our findings may help identify patients at greatest risk of illness secondary to a respiratory virus, anticipate hospital resource needs, and prioritize local prevention and therapeutic strategies to communities with higher prevalence of risk factors.

Analysing the protection from respiratory tract infections and allergic diseases early in life by human milk components: the PRIMA birth cohort

Background

Many studies support the protective effect of breastfeeding on respiratory tract infections. Although infant formulas have been developed to provide adequate nutritional solutions, many components in human milk contributing to the protection of newborns and aiding immune development still need to be identified. In this paper we present the methodology of the “Protecting against Respiratory tract lnfections through human Milk Analysis” (PRIMA) cohort, which is an observational, prospective and multi-centre birth cohort aiming to identify novel functions of components in human milk that are protective against respiratory tract infections and allergic diseases early in life.

Methods

For the PRIMA human milk cohort we aim to recruit 1000 mother–child pairs in the first month postpartum. At one week, one, three, and six months after birth, fresh human milk samples will be collected and processed. In order to identify protective components, the level of pathogen specific antibodies, T cell composition, Human milk oligosaccharides, as well as extracellular vesicles (EVs) will be analysed, in the milk samples in relation to clinical data which are collected using two-weekly parental questionnaires. The primary outcome of this study is the number of parent-reported medically attended respiratory infections. Secondary outcomes that will be measured are physician diagnosed (respiratory) infections and allergies during the first year of life.

Discussion

The PRIMA human milk cohort will be a large prospective healthy birth cohort in which we will use an integrated, multidisciplinary approach to identify the longitudinal effect human milk components that play a role in preventing (respiratory) infections and allergies during the first year of life. Ultimately, we believe that this study will provide novel insights into immunomodulatory components in human milk. This may allow for optimizing formula feeding for all non-breastfed infants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07107-w.

Evaluation of the ImmuView RSV Test for Rapid Detection of Respiratory Syncytial Virus in Adult Patients with Influenza-Like Symptoms

Rapid antigen tests may enhance the diagnostic yield of respiratory syncytial virus (RSV) infections, but studies have shown low sensitivity in adults. We evaluated the novel ImmuView RSV test in adult patients with influenza-like symptoms who were prospectively enrolled at three emergency departments in two Swedish hospitals during two influenza seasons, 2017 to 2018 and 2018 to 2019. The ImmuView RSV test was performed on nasopharyngeal swabs and results were compared to those of the BinaxNOW RSV test. In the first season, tests were performed on frozen samples, while unfrozen samples were used in the second season. For comparison, tests were also performed on selected samples from children. Of 333 included adult patients, the sensitivity of ImmuView and BinaxNOW was 27% for both tests and specificities were 98% and 100%, respectively. The interassay agreement was good (κ = 0.61). There was no significant difference in test performance between frozen and unfrozen samples. In samples from children, the sensitivities of ImmuView and BinaxNOW were 67% and 70%, respectively. In conclusion, the ImmuView RSV test showed low sensitivity and high specificity for identifying RSV in adult patients with influenza-like symptoms, comparable with the BinaxNOW RSV test. Rapid RSV testing is of limited value for diagnosing RSV infection in adults. IMPORTANCE By timely RSV diagnosis among patients with influenza-like symptoms, especially when influenza diagnostics turn negative, it is possible to prevent unnecessary antibiotic usage as well as reduce diagnostic testing, nosocomial transmission, and hospital stay. Previous rapid RSV tests have demonstrated poor sensitivity in adults, and we could demonstrate that the novel ImmuView RSV test similarly showed limited value for diagnosing RSV infection in adult patients. However, in contrast to many other studies, we investigated patient characteristics in cases with false-positive tests and we compared the performance between unfrozen and frozen samples. Thus, our results are important, as they generate new knowledge about rapid antigen tests.

Respiratory Syncytial Virus

Human respiratory syncytial virus (RSV) is a negative sense single-stranded RNA virus that can result in epidemics of seasonal respiratory infections. Generally, one of the two genotypes (A and B) predominates in a single season and alternate annually with regional variation. RSV is a known cause of disease and death at both extremes of ages in the pediatric and elderly, as well as immunocompromised populations. The clinical impact of RSV on the hospitalized adults has been recently clarified with the expanded use of multiplex molecular assays. Among adults, RSV can produce a wide range of clinical symptoms due to upper respiratory tract infections potentially leading to severe lower respiratory tract infections, as well as exacerbations of underlying cardiac and lung diseases. While supportive care is the mainstay of therapy, there are currently multiple therapeutic and preventative options under development.

Analysis of the adverse events following immunization with inactivated quadrivalent influenza vaccine from 2018 to 2020 in Zhejiang province, with a comparison to trivalent influenza vaccine

OBJECTIVES

To summarize reports to the national adverse event following immunization surveillance system (NAEFISS) following inactivated quadrivalent influenza vaccine (QIV) in Zhejiang province from 2018 to 2020.

METHODS

We analyzed adverse events following immunization (AEFI) reports following QIV, with a comparison, with the AEFI reports following inactivated trivalent influenza vaccine (TIV). Reporting rates of AEFI were calculated by age, severity of AEFI, categories of AEFI, and reaction categories. The data mining algorithm used in this study was reporting odds ratio (ROR). A value of ROR‑1.96SE >1 (standard error [SE]) was considered as positive signal. These reporting rates between vaccine types were compared through chi-square tests.

RESULTS

NAEFISS received 514 AEFI reports following QIV and 536 reports following TIV, with a reporting rate of 13.66/100,000 100,000 doses/100,000 doses (χ² = 7.11, P> .05). Of the 514 reports following QIV, 410 were vaccine product-related reactions and 51 were severe AEFI. Fever/redness/induration was the most frequent clinical diagnosis of the QIV AEFI, with a reporting rate of 12.42/100,000 doses in the age group of 3-17 years, and 12.44/100,000 doses in the age group of ≥18 years. The positive signal of QIV AEFI was observed for the allergic rash and asthma/wheezing.

CONCLUSION

The present analysis did not identify any new/unexpected safety concerns. We suggested that NAEFISS continue to monitor the safety of QIV.

Priorities for developing respiratory syncytial virus vaccines in different target populations

The development of an effective vaccine against respiratory syncytial virus (RSV) has been hampered by major difficulties that occurred in the 1960s when a formalin-inactivated vaccine led to increased severity of RSV disease after acquisition of the virus in the RSV season after vaccination. Recent renewed efforts to develop a vaccine have resulted in about 38 candidate vaccines and monoclonal antibodies now in clinical development. The target populations for effective vaccination are varied and include neonates, young children, pregnant women, and older adults. The reasons for susceptibility to infection in each of these groups may be different and, therefore, could require different vaccine types for induction of protective immune responses, adding a further challenge for vaccine development. Here, we review the current knowledge of RSV vaccine development for these target populations and propose a view and rationale for prioritizing RSV vaccine development.

Young infants exhibit robust functional antibody responses and restrained IFN-γ production to SARS-CoV-2

Severe COVID-19 appears rare in children. This is unexpected, especially in young infants, who are vulnerable to severe disease caused by other respiratory viruses. We evaluate convalescent immune responses in 4 infants under 3 months old with confirmed COVID-19 who presented with mild febrile illness, alongside their parents, and adult controls recovered from confirmed COVID-19. Although not statistically significant, compared to seropositive adults, infants have high serum levels of IgG and IgA to SARS-CoV-2 spike protein, with a corresponding functional ability to block SARS-CoV-2 cellular entry. Infants also exhibit robust saliva anti-spike IgG and IgA responses. Spike-specific IFN-γ production by infant peripheral blood mononuclear cells appears restrained, but the frequency of spike-specific IFN-γ- and/or TNF-α-producing T cells is comparable between infants and adults. On principal-component analysis, infant immune responses appear distinct from their parents. Robust functional antibody responses alongside restrained IFN-γ production may help protect infants from severe COVID-19.

Regulatory KIR+ RA+ T cells accumulate with age and are highly activated during viral respiratory disease

Severe respiratory viral infectious diseases such as influenza and COVID‐19 especially affect the older population. This is partly ascribed to diminished CD8⁺ T‐cell responses a result of aging. The phenotypical diversity of the CD8⁺ T‐cell population has made it difficult to identify the impact of aging on CD8⁺ T‐cell subsets associated with diminished CD8⁺ T‐cell responses. Here we identify a novel human CD8⁺ T‐cell subset characterized by expression of Killer‐cell Immunoglobulin‐like Receptors (KIR⁺) and CD45RA (RA⁺). These KIR⁺RA⁺ T cells accumulated with age in the blood of healthy individuals (20–82 years of age, n = 50), expressed high levels of aging‐related markers of T‐cell regulation, and were functionally capable of suppressing proliferation of other CD8⁺ T cells. Moreover, KIR⁺RA⁺ T cells were a major T‐cell subset becoming activated in older adults suffering from an acute respiratory viral infection (n = 36), including coronavirus and influenza virus infection. In addition, older adults with influenza A infection showed that higher activation status of their KIR⁺RA⁺ T cells associated with longer duration of respiratory symptoms. Together, our data indicate that KIR⁺RA⁺ T cells are a unique human T‐cell subset with regulatory properties that may explain susceptibility to viral respiratory disease at old age.

Comparison of clinical characteristics and outcomes between respiratory syncytial virus and influenza-related pneumonia in China from 2013 to 2019

This study aims to compare clinical characteristics and severity between adults with respiratory syncytial virus (RSV-p) and influenza-related pneumonia (Flu-p). A total of 127 patients with RSV-p, 693 patients with influenza A-related pneumonia (FluA-p), and 386 patients with influenza B-related pneumonia (FluB-p) were retrospectively reviewed from 2013 through 2019 in five teaching hospitals in China. A multivariate logistic regression model indicated that age ≥ 50 years, cerebrovascular disease, chronic kidney disease, solid malignant tumor, nasal congestion, myalgia, sputum production, respiratory rates ≥ 30 beats/min, lymphocytes < 0.8×10⁹/L, and blood albumin < 35 g/L were predictors that differentiated RSV-p from Flu-p. After adjusting for confounders, a multivariate logistic regression analysis confirmed that, relative to RSV-p, FluA-p (OR 2.313, 95% CI 1.377–3.885, p = 0.002) incurred an increased risk for severe outcomes, including invasive ventilation, ICU admission, and 30-day mortality; FluB-p (OR 1.630, 95% CI 0.958–2.741, p = 0.071) was not associated with increased risk. Some clinical variables were useful for discriminating RSV-p from Flu-p. The severity of RSV-p was less than that of FluA-p, but was comparable to FluB-p.

Detection of influenza virus in air samples of patient rooms

BACKGROUND

Understanding the transmission and dispersal of influenza virus and respiratory syncytial virus (RSV) via aerosols is essential for the development of preventative measures in hospital environments and healthcare facilities.

METHODS

During the 2017-2018 influenza season, patients with confirmed influenza or RSV infections were enrolled. Room air samples were collected close (0.30 m) to and distant (2.20 m) from patients' heads. Real-time polymerase chain reaction was used to detect and quantify viral particles in the air samples. The plaque assay was used to determine the infectiousness of the detected viruses.

FINDINGS

Fifty-one air samples were collected from the rooms of 29 patients with laboratory-confirmed influenza; 51% of the samples tested positive for influenza A virus (IAV). Among the IAV-positive patients, 65% were emitters (had at least one positive air sample), reflecting a higher risk of nosocomial transmission compared with non-emitters. The majority (61.5%) of the IAV-positive air samples were collected 0.3 m from a patient's head, while the remaining IAV-positive air samples were collected 2.2 m from a patient's head. The positivity rate of IAV in air samples was influenced by distance from the patient's head and day of sample collection after hospital admission. Only three patients with RSV infection were recruited and none of them were emitters.

CONCLUSION

Influenza virus can be aerosolized beyond 1 m in patient rooms, which is the distance considered to be safe by infection control practices. Further investigations are needed to determine the extent of infectivity of aerosolized virus particles.

First contact: the role of respiratory cilia in host-pathogen interactions in the airways

Respiratory cilia are the driving force of the mucociliary escalator, working in conjunction with secreted airway mucus to clear inhaled debris and pathogens from the conducting airways. Respiratory cilia are also one of the first contact points between host and inhaled pathogens. Impaired ciliary function is a common pathological feature in patients with chronic airway diseases, increasing susceptibility to respiratory infections. Common respiratory pathogens, including viruses, bacteria, and fungi, have been shown to target cilia and/or ciliated airway epithelial cells, resulting in a disruption of mucociliary clearance that may facilitate host infection. Despite being an integral component of airway innate immunity, the role of respiratory cilia and their clinical significance during airway infections are still poorly understood. This review examines the expression, structure, and function of respiratory cilia during pathogenic infection of the airways. This review also discusses specific known points of interaction of bacteria, fungi, and viruses with respiratory cilia function. The emerging biological functions of motile cilia relating to intracellular signaling and their potential immunoregulatory roles during infection will also be discussed.

Lung innervation in the eye of a cytokine storm: neuroimmune interactions and COVID-19

COVID-19 is an infectious disease caused by the coronavirus SARS-CoV-2, which was first reported in Wuhan, China, in December 2019 and has caused a global pandemic. Acute respiratory distress syndrome (ARDS) is a common feature of severe forms of COVID-19 and can lead to respiratory failure, especially in older individuals. The increasing recognition of the neurotropic potential of SARS-CoV-2 has sparked interest in the role of the nervous system in respiratory failure in people with COVID-19. However, the neuroimmune interactions in the lung in the context of ARDS are poorly understood. In this Perspectives article, we propose the concept of the neuroimmune unit as a critical determinant of lung function in the context of COVID-19, inflammatory conditions and ageing, focusing particularly on the involvement of the vagus nerve. We discuss approaches such as neurostimulation and pharmacological neuromodulation to reduce tissue inflammation with the aim of preventing respiratory failure.

Acute respiratory distress syndrome is a common occurrence in COVID-19, an infectious disease caused by the coronavirus SARS-CoV-2. In this article, the authors consider how lung innervation might crosstalk with the immune system to modulate lung function and influence outcomes in COVID-19.

Cost-effectiveness of inactivated influenza vaccination in children with medical risk conditions in the Netherlands

BACKGROUND

In many countries, annual immunization with inactivated influenza vaccine (IIV) is recommended for children with medical risk conditions. Prior cost-effectiveness analyses found such immunization to be cost saving, but assumed effectiveness against non-severe influenza outcomes and a higher effectiveness against severe influenza outcomes than recent studies would suggest. However, recent vaccine studies do not indicate any reduction in community or outpatient disease episodes in IIV immunized individuals. We therefore evaluated cost-effectiveness of IIV immunization in children with medical risk conditions in the Netherlands, assuming that IIV reduces influenza-related hospitalization and death, but has no meaningful impact on non-severe health outcomes.

METHODS

A health economic decision tree model was developed to evaluate health effects and costs of annual IIV immunization versus no immunization. Model inputs were based on our study on influenza-related primary care visits and other literature. Immunization was considered cost effective if associated costs were less than €20,000 per quality-adjusted life year (QALY) gained. Probabilistic sensitivity analyses were performed to assess robustness of results, and one-way sensitivity analyses and scenario analyses were done to assess the influence of individual parameters.

RESULTS

Annual IIV prevents an average of 1.59 influenza-related hospitalizations and 0.02 deaths per 1,000 children with medical risk conditions. This results in an expected QALY gain of 0.43 at incremental costs of €21,564 per 1,000 children, corresponding to an incremental cost-effectiveness ratio (ICER) of €50,297/QALY compared to no immunization. Under base case assumptions, immunization had a 5% probability of being cost effective. Results were most influenced by vaccine efficacy against fatal influenza, QALY loss due to death, and mortality rate.

CONCLUSIONS

If IIV only reduces severe disease outcomes, as current evidence suggests, annual immunization of medical risk children is unlikely to be cost effective. Results should however be interpreted with caution as cost-effectiveness is largely dependent on incidence and QALY losses for fatal influenza, for which evidence is scarce.

Antiviral activity of ethanol extract of Lophatherum gracile against respiratory syncytial virus infection

ETHNOPHARMACOLOGICAL RELEVANCE

Lophatherum gracile, an important medicinal plant, is used traditionally in the treatment of cough associated with lung heat and inflammation. In this study, an ethanol extract of L. gracile (DZY) was shown to inhibit respiratory syncytial virus (RSV) infection and RSV-induced inflammation in vitro and in vivo. These findings provide a strong and powerful support for the traditional use of L. gracile in the treatment of RSV-related diseases.

AIM OF THE STUDY

To determine the anti-RSV activities of DZY and its ingredients, and explore the relationship between RSV infection and inflammation.

MATERIALS AND METHODS

DZY was extracted from L. gracile and its major ingredients were determined by high-performance liquid chromatography (HPLC). RSV-infected HEp-2 and RAW264.7 cell models were established to assess the inhibitory effect of DZY on RSV replication and nitric oxide (NO) production in vitro. Three-week-old BALB/c mice challenged intranasally with RSV were used to establish RSV-infected animal mode. The mice were respectively administered DZY at high-, middle-, and low-dose in different groups. The anti-RSV activity of DZY was evaluated by detecting viral load, lung lesion, CD4⁺ and CD8⁺ T cell population, and interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ expression in the lung tissue.

RESULTS

In HEp-2 cell line, DZY effectively inhibited RSV infection in a dose-dependent manner with IC₅₀ values of 20 μg/mL against RSV (Long strain) and IC₅₀ values of 25 μg/mL against RSV (A2 strain). The anti-RSV activity of DZY was mainly determined by isoorientin, swertiajaponin, 3, 5-di-caffeoylquinic acid, and 3, 4-di-caffeoylquinic acid. Moreover, DZY suppressed NO production induced by RSV in vitro. In vivo, oral administration of DZY significantly reduced the viral load and ameliorated lesions in the lung tissue. A probable antiviral mechanism was mediated by slightly improving the ratio of CD4⁺/CD8⁺ T cells and inhibiting the mRNA and protein expression of IL-1β, TNF-α, and IFN-γ.

CONCLUSIONS

(1) DZY exhibits anti-RSV activities both in vitro and in vivo. (2) RSV infection can trigger a series of inflammatory reactions; thus, ameliorating inflammation is helpful to control the course of disease caused by RSV. These findings provide the rationale and scientific evidence behind the extensive use of L. gracile in traditional medicine for the treatment of diseases potentially caused by RSV.

Respiratory syncytial virus infection in adults

Human respiratory syncytial virus (RSV) belongs to the recently defined Pneumoviridae family, Orthopneumovirus genus. It is a negative sense, single stranded RNA virus that results in epidemics of respiratory infections that typically peak in the winter in temperate climates and during the rainy season in tropical climates. Generally, one of the two genotypes (A and B) predominates in a single season, alternating annually, although regional variation occurs. RSV is a cause of disease and death in children, older people, and immunocompromised patients, and its clinical effect on adults admitted to hospital is clarified with expanded use of multiplex molecular assays. Among adults, RSV produces a wide range of clinical symptoms including upper respiratory tract infections, severe lower respiratory tract infections, and exacerbations of underlying disease. Here we discuss the latest evidence on the burden of RSV related disease in adults, especially in those with immunocompromise or other comorbidities. We review current therapeutic and prevention options, as well as those in development.

Influenza vaccination in the elderly: 25 years follow-up of a randomized controlled trial. No impact on long-term mortality

Influenza vaccination is proven effective in preventing influenza. However, long-term effects on mortality have never been supported by direct evidence. In this study we assessed the long-term outcome of influenza vaccination on mortality in the elderly by conducting a 25-year follow-up study of a RCT on the efficacy of influenza vaccination as baseline. The RCT had been conducted in the Netherlands 5 years before vaccination was recommended for those aged >65 and 17 years before recommending it for those aged >60. The RCT included 1838 community-dwelling elderly aged ≥ 60 that had received an intramuscular injection with the inactivated quadrivalent influenza vaccine (n = 927) or placebo (n = 911) during the 1991/1992 winter. In our follow-up study, outcomes included all-cause mortality, influenza-related mortality and seasonal mortality. Unadjusted and adjusted hazard ratios (HRs) were estimated by Cox regression and sub-hazard ratios (SHRs) by competing risk models. Secondary analyses included subgroup analyses by age and disease status. The vital status up to January 1, 2017 was provided in 1800/1838 (98%) of the cases. Single influenza vaccination did not reduce all-cause mortality when compared to placebo (adjusted HR 0.95, 95% CI 0.85−1.05). Also, no differences between vaccination and placebo group were shown for underlying causes of death or seasonal mortality. In those aged 60–64, median survival increased with 20.1 months (95% CI 2.4–37.9), although no effects on all-cause mortality (adjusted HR 0.86, 95% CI 0.72−1.03) could be demonstrated in survival analysis. In conclusion, this study did not demonstrate a statistically significant effect following single influenza vaccination on long-term mortality in community-dwelling elderly in general. We propose researchers designing future studies on influenza vaccination in the elderly to fit these studies for longer-term follow-up, and suggest age-group comparisons in observational research.

Clinical trial registry number:NTR6179.

Analysis of acute respiratory infections due to influenza virus A, B and RSV during an influenza epidemic 2018

PURPOSE

We studied the incidence, morbidity and mortality of all patients presenting in our teaching hospital with proven influenza virus and/or respiratory syncytial virus (RSV) infection during the influenza epidemic season 2018 which was characterized by a predominant incidence of influenza virus B type B of the Yamagata line.

METHODS

In the fall of 2017, specific precaution measures in addition to standard measures were implemented, including standardized testing for influenza virus A,B and RSV by multiplex PCR of pharyngeal swabsData from all consecutive patients were analyzed retrospectively.

RESULTS

Overall 651 patients were examined for the presence of influenza virus and RSV; 214 patients had influenza virus A (n = 36), B (n = 152), and/or RSV (n = 30), including four patients with dual infection. 86% of cases had influenza virus (80% B), and 14% RSV infection. N = 23 cases were treated as outpatients. The rate of acute viral respiratory infections (influenza virus and RSV) was 191 of 2776 (6.9%) admissions to medical wards. Of n = 191 hospitalized cases, n = 44 cases (20.6%) had nosocomial infection. Viral infections were associated with a high morbidity (pneumonia 28.5%, mortality 4.7%). Independent predictors of prolonged hospitalization were the presence of pneumonia, NIV and renal complications, and independent predictors of pneumonia were age ≥ 65 years, bedridden status and CRP ≥ 2.9 mg/dL.

CONCLUSIONS

The rate of nosocomial cases was high despite established precaution measures. RSV was associated with morbidity and mortality comparable to influenza. Pneumonia remains the main complication of acute viral respiratory infections, and antimicrobial treatment should include both antiviral as well as antibacterial agents.

Transcriptomics in lung tissue upon respiratory syncytial virus infection reveals aging as important modulator of immune activation and matrix maintenance

Aging poses an increased risk of severe infection by respiratory syncytial virus (RSV). The many different biological pathways comprising the response to infection in lungs that are influenced by aging are complex and remain to be defined more thoroughly. Towards finding new directions in research on aging, we aimed to define biological pathways in the acute response to RSV that are affected in the lungs by aging. We therefore profiled the full transcriptome of lung tissue of mice prior to and during RSV infection both at young and old age. In the absence of RSV, we found aging to downregulate genes that are involved in constitution of the extracellular matrix. Moreover, uninfected old mice showed elevated expression of pathways that resemble injury, metabolic aberrations, and disorders mediated by functions of the immune system that were induced at young age only by an exogenous trigger like RSV. Furthermore, infection by RSV mounted stronger activation of anti-viral type-I interferon pathways at old age. Despite such exaggerated anti-viral responses, old mice showed reduced control of virus. Altogether, our findings emphasize important roles in aging-related susceptibility to respiratory disease for extracellular matrix dysfunctions and dysregulated immune activation in lungs.

Safety, Tolerability and Pharmacokinetics of MEDI8897, an Extended Half-life Single-dose Respiratory Syncytial Virus Prefusion F-targeting Monoclonal Antibody Administered as a Single Dose to Healthy Preterm Infants

BACKGROUND

MEDI8897 is a recombinant human monoclonal antibody being developed for prophylaxis of serious respiratory syncytial virus (RSV) disease in all infants.

METHODS

In this phase 1b/2a dose-escalation study, healthy preterm infants with a gestational age of 32-35 weeks were randomized to receive a single intramuscular injection of MEDI8897 (10, 25 or 50 mg) or placebo. Safety, pharmacokinetics, RSV-neutralizing antibody and antidrug antibody (ADA) assessments were performed during the 360-day follow-up period. Infants who experienced medically attended lower respiratory tract infections (LRTIs) were tested for RSV.

RESULTS

MEDI8897 serum half-life ranged from 62.5-72.9 days. On day 151, 87% of infants in the 50 mg group had serum concentrations above the 90% effective concentration target level of 6.8 µg/mL, and 90% showed a ≥4-fold rise from baseline in serum RSV-neutralizing antibody levels. Adverse events (AEs) were reported in 17 of 18 (94.4%) placebo and 66 of 71 (93.0%) MEDI8897 recipients. Three MEDI8897 recipients experienced 5 serious AEs (3 LRTIs, 2 febrile seizures). ADA was detected at any time postbaseline in 28.2% of MEDI8897 recipients and at day 361 only in 26.5% of subjects. ADA response was not associated with AEs. Five (7%) MEDI8897 recipients experienced medically attended LRTIs through day 150; 1 tested positive for RSV (10 mg group).

CONCLUSIONS

MEDI8897 had a favorable safety profile in healthy preterm infants. The extended half-life of MEDI8897 and demonstrated RSV-neutralizing activity support protection from RSV for the duration of a typical 5-month season after a single 50 mg intramuscular (IM) dose.

Cytokines and CD8 T cell immunity during respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection and hospitalization in infants. In spite of the enormous clinical burden caused by RSV infections, there remains no efficacious RSV vaccine. CD8 T cells mediate viral clearance as well as provide protection against a secondary RSV infection. However, RSV-specific CD8 T cells may also induce immunopathology leading to exacerbated morbidity and mortality. Many of the crucial functions performed by CD8 T cells are mediated by the cytokines they produce. IFN-γ and TNF are produced by CD8 T cells following RSV infection and contribute to both the acceleration of viral clearance and the induction of immunopathology. To prevent immunopathology, regulatory mechanisms are in place within the immune system to inhibit CD8 T cell effector functions after the infection has been cleared. The actions of a variety of cytokines, including IL-10 and IL-4, play a critical role in the regulation of CD8 T cell effector activity. Herein, we review the current literature on CD8 T cell responses and the functions of the cytokines they produce following RSV infection. Additionally, we discuss the regulation of CD8 T cell activation and effector functions through the actions of various cytokines.

A multifunctional human monoclonal neutralizing antibody that targets a unique conserved epitope on influenza HA

The high rate of antigenic drift in seasonal influenza viruses necessitates frequent changes in vaccine composition. Recent seasonal H3 vaccines do not protect against swine-origin H3N2 variant (H3N2v) strains that recently have caused severe human infections. Here, we report a human V_H1-69 gene-encoded monoclonal antibody (mAb) designated H3v-47 that exhibits potent cross-reactive neutralization activity against human and swine H3N2 viruses that circulated since 1989. The crystal structure and electron microscopy reconstruction of H3v-47 Fab with the H3N2v hemagglutinin (HA) identify a unique epitope spanning the vestigial esterase and receptor-binding subdomains that is distinct from that of any known neutralizing antibody for influenza A H3 viruses. MAb H3v-47 functions largely by blocking viral egress from infected cells. Interestingly, H3v-47 also engages Fcγ receptor and mediates antibody dependent cellular cytotoxicity (ADCC). This newly identified conserved epitope can be used in design of novel immunogens for development of broadly protective H3 vaccines.

Broadly neutralizing antibodies are potential therapeutics and can aid rational vaccine development. Here, the authors show that the human monoclonal antibody H3v-47 recognizes a highly conserved epitope in HA of H3N2 viruses, inhibits virus replication by blocking egress and other mechanisms, and protects mice from disease.

Diversity of aging of the immune system classified in the cotton rat (Sigmodon hispidus) model of human infectious diseases

Susceptibility and declined resistance to human pathogens like respiratory syncytial virus (RSV) at old age is well represented in the cotton rat (Sigmodon hispidus). Despite providing a preferred model of human infectious diseases, little is known about aging of its adaptive immune system. We aimed to define aging-related changes of the immune system of this species. Concomitantly, we asked whether the rate of immunological alterations may be stratified by physiological aberrations encountered during aging. With increasing age, cotton rats showed reduced frequencies of T cells, impaired induction of antibodies to RSV, higher incidence of aberrations of organs and signs of lipemia. Moreover, old animals expressed high biological heterogeneity, but the age-related reduction of T cell frequency was only observed in those specimens that displayed aberrant organs. Thus, cotton rats show age-related alterations of lymphocytes that can be classified by links with health status.

The CD8 T Cell Response to Respiratory Virus Infections

Humans are highly susceptible to infection with respiratory viruses including respiratory syncytial virus (RSV), influenza virus, human metapneumovirus, rhinovirus, coronavirus, and parainfluenza virus. While some viruses simply cause symptoms of the common cold, many respiratory viruses induce severe bronchiolitis, pneumonia, and even death following infection. Despite the immense clinical burden, the majority of the most common pulmonary viruses lack long-lasting efficacious vaccines. Nearly all current vaccination strategies are designed to elicit broadly neutralizing antibodies, which prevent severe disease following a subsequent infection. However, the mucosal antibody response to many respiratory viruses is not long-lasting and declines with age. CD8 T cells are critical for mediating clearance following many acute viral infections in the lung. In addition, memory CD8 T cells are capable of providing protection against secondary infections. Therefore, the combined induction of virus-specific CD8 T cells and antibodies may provide optimal protective immunity. Herein, we review the current literature on CD8 T cell responses induced by respiratory virus infections. Additionally, we explore how this knowledge could be utilized in the development of future vaccines against respiratory viruses, with a special emphasis on RSV vaccination.

Heterogeneity in Estimates of the Impact of Influenza on Population Mortality: A Systematic Review

Influenza viruses are associated with a substantial global burden of morbidity and mortality every year. Estimates of influenza-associated mortality often vary between studies due to differences in study settings, methods, and measurement of outcomes. We reviewed 103 published articles assessing population-based influenza-associated mortality through searches of PubMed and Embase, and we identified considerable variation in the statistical methods used across studies. Studies using regression models with an influenza activity proxy applied 4 approaches to estimate influenza-associated mortality. The estimates increased with age and ranged widely, from -0.3-1.3 and 0.6-8.3 respiratory deaths per 100,000 population for children and adults, respectively, to 4-119 respiratory deaths per 100,000 population for older adults. Meta-regression analysis identified that study design features were associated with the observed variation in estimates. The estimates increased with broader cause-of-death classification and were higher for older adults than for children. The multiplier methods tended to produce lower estimates, while Serfling-type models were associated with higher estimates than other methods. No "average" estimate of excess mortality could reliably be made due to the substantial variability of the estimates, partially attributable to methodological differences in the studies. Standardization of methodology in estimation of influenza-associated mortality would permit improved comparisons in the future.

Excess pneumonia and influenza hospitalizations associated with influenza epidemics in Portugal from season 1998/1999 to 2014/2015

BACKGROUND

The aim of this study was to estimate excess pneumonia and influenza (P&I) hospitalizations during influenza epidemics and measure their correlation with influenza vaccine coverage in the 65 and more years old, according to the type/subtype of influenza virus.

METHODS

The study period comprised week 40/1998-40/2015. Age-specific weekly P&I hospitalizations (ICD-9: 480-487) as main diagnosis were extracted from the National Hospital Discharge database. Age-specific baseline hospitalization rates were estimated by autoregressive integrated moving average (ARIMA) model without time periods with excess hospitalizations. Excess hospitalizations were calculated by subtracting expected hospitalization rates from the observed during influenza epidemic periods. Correlation between excess P&I hospitalizations and influenza vaccine coverage in the elderly was measured with Pearson correlation coefficient.

RESULTS

The average excess P&I hospitalizations/season was 19.4/105 (range 0-46.1/105 ), and higher excess was observed in young children with <2 years (79.8/105 ) and ≥65 years (68.3/105 ). In epidemics with A(H3) dominant, the highest excess hospitalizations were observed among 65 and over. Seasons which influenza B or A(H1)pdm09 dominance the highest excess was observed in children with <2 years. High negative correlation was estimated between excess hospitalizations associated with A(H3) circulation and vaccine coverage in the elderly (r = -.653; 95% CI: -0.950 to -0.137).

CONCLUSION

Over 80% of the influenza epidemics were associated with excess hospitalizations. However, excess P&I hospitalizations pattern differed from age group and circulating virus. This ecologic approach also identified a reduction in excess P&I associated with A(H3) circulation with increasing vaccine coverage in the elderly.

Cost-effectiveness of rule-based immunoprophylaxis against respiratory syncytial virus infections in preterm infants

The objective of the paper is to assess the cost-effectiveness of targeted respiratory syncytial virus (RSV) prophylaxis based on a validated prediction rule with 1-year time horizon in moderately preterm infants compared to no prophylaxis. Data on health care consumption were derived from a randomised clinical trial on wheeze reduction following RSV prophylaxis and a large birth cohort study on risk prediction of RSV hospitalisation. We calculated the incremental cost-effectiveness ratio (ICER) of targeted RSV prophylaxis vs. no prophylaxis per quality-adjusted life year (QALYs) using a societal perspective, including medical and parental costs and effects. Costs and health outcomes were modelled in a decision tree analysis with sensitivity analyses. Targeted RSV prophylaxis in infants with a first-year RSV hospitalisation risk of > 10% resulted in a QALY gain of 0.02 (0.931 vs. 0.929) per patient against additional cost of €472 compared to no prophylaxis (ICER €214,748/QALY). The ICER falls below a threshold of €80,000 per QALY when RSV prophylaxis cost would be lowered from €928 (baseline) to €406 per unit. At a unit cost of €97, RSV prophylaxis would be cost saving.

CONCLUSIONS

Targeted RSV prophylaxis is not cost-effective in reducing RSV burden of disease in moderately preterm infants, but it can become cost-effective if lower priced biosimilar palivizumab or a vaccine would be available.

Risk of mortality associated with respiratory syncytial virus and influenza infection in adults

Background

Respiratory syncytial virus (RSV) infection constitutes a substantial disease burden in the general population. However, the risk of death for RSV infection has been rarely evaluated with confounders or comorbidities adjusted. We aimed to evaluate whether RSV infection is associated with higher mortality than seasonal influenza after adjusting for confounders and comorbidities and the effect of oseltamivir on the mortality in patients with influenza infection.

Methods

A retrospective cohort study was conducted on adult (≥18 years) patients admitted to the emergency department and ward of a university teaching hospital for suspected viral infection during 2013–2015 (N = 3743). RSV infection was diagnosed by multiplex PCR (N = 87). Adults hospitalized for seasonal influenza during the study period were enrolled as a comparison group (n = 312). The main outcome was 20-day all-cause mortality.We used Cox proportional hazard regression analyses to calculate the relative risk of death.

Results

Adult patients were less likely to be diagnosed with RSV than with influenza (2.3 vs 8.3%, respectively), were older and more likely to be diagnosed with pneumonia, chronic obstructive pulmonary disease, hypoxemia, and bacterial co-infection. In patients with RSV infection, the 20-day all-cause mortality was higher than that for influenza, (18.4 vs 6.7%, respectively). RSV infection showed significantly higher risk of death compared to the seasonal influenza group, with hazard ratio, 2.32 (95% CI, 1.17–4.58). Oseltamivir had no significant effect on mortality in patients with influenza.

Conclusions

RSV infection was significantly associated with a higher risk of death than seasonal influenza, adjusted for potential confounders and comorbidities.

Healthcare-seeking behaviour in case of influenza-like illness in the French general population and factors associated with a GP consultation: an observational prospective study

Background

GP consultation rates for influenza-like illness (ILI) are poorly known in France and there is a paucity of literature on this topic. In the few articles that have been published, the results are heterogeneous.

Aim

The aim of the present study was to estimate the proportion of ILI inducing a GP consultation, and to assess its determinants.

Design & setting

Participants of a French web-based cohort study who reported ≥1 ILI episode between 2012 and 2015 were included. Sociodemographic characteristics, access to health care, and health status variables were collected.

Method

Healthcare-seeking behaviour was analysed and factors associated with a GP consultation identified using a conditional logistic regression.

Results

Of the 6023 ILI episodes reported, 1961 (32.6%) led to a GP consultation, with no difference between those at risk of influenza complications and those not (P = 0.42). A GP consultation was more frequent for individuals living in a rural area (odds ratio [OR] = 1.21, 95% confidence interval [CI] = 1.02 to 1.43); those with a lower educational level (OR = 1.43, 95% CI = 1.18 to 1.74); those using the internet to find information about influenza (OR = 1.63, 95% CI = 1.30 to 2.03); patients presenting with worrying symptoms (fever, cough, dyspnoea, sputum, or asthenia); patients having a negative perception of their own health status (OR = 1.51, 95% CI = 1.07 to 2.13; and those having declared a personal doctor (OR = 2.86, 95% CI = 1.72 to 4.76). A GP consultation was less frequent for individuals using alternative medicine (OR = 0.68, 95% CI = 0.58 to 0.78).

Conclusion

This study allows the identification of specific factors associated with GP consultation for an ILI episode. These findings may help to coordinate health information campaigns and to raise awareness, especially among individuals at risk of influenza complications.

New Insights Contributing to the Development of Effective Vaccines and Therapies to Reduce the Pathology Caused by hRSV

Human Respiratory Syncytial Virus (hRSV) is one of the major causes of acute lower respiratory tract infections (ALRTI) worldwide, leading to significant levels of immunocompromisation as well as morbidity and mortality in infants. Its main target of infection is the ciliated epithelium of the lungs and the host immune responses elicited is ineffective at achieving viral clearance. It is thought that the lack of effective immunity against hRSV is due in part to the activity of several viral proteins that modulate the host immune response, enhancing a Th2-like pro-inflammatory state, with the secretion of cytokines that promote the infiltration of immune cells to the lungs, with consequent damage. Furthermore, the adaptive immunity triggered by hRSV infection is characterized by weak cytotoxic T cell responses and secretion of low affinity antibodies by B cells. These features of hRSV infection have meant that, to date, no effective and safe vaccines have been licensed. In this article, we will review in detail the information regarding hRSV characteristics, pathology, and host immune response, along with several prophylactic treatments and vaccine prototypes. We will also expose significant data regarding the newly developed BCG-based vaccine that promotes protective cellular and humoral response against hRSV infection, which is currently undergoing clinical evaluation.

The epidemiology of medically attended respiratory syncytial virus in older adults in the United States: A systematic review

Objective

This review was undertaken to assess the historical evidence of the disease incidence and burden of laboratory-confirmed respiratory syncytial virus (RSV) in medically attended older adults.

Design

A qualitative systematic literature review was performed; no statistical synthesis of the data was planned, in anticipation of expected heterogeneity across studies in this population.

Methods

A literature search of PubMed, Embase, and the Cochrane Library was conducted for studies of medically attended RSV in older adults (≥ 50 years) published in the last 15 years. Two independent reviewers screened titles and abstracts based on predefined inclusion and exclusion criteria.

Results

From 10 studies reporting incidence proportions, RSV may be the causative agent in up to 12% of medically attended acute respiratory illness in older adults unselected for comorbidities, with variations in clinical setting and by year. In multiple studies, medically attended–RSV incidence among older adults not selected for having underlying health conditions increased with increasing age. Of prospectively followed lung transplant recipients, 16% tested positive for RSV. In hospitalized adults with chronic cardiopulmonary diseases, 8% to 13% were infected with RSV during winter seasons (8%-13%) or metapneumovirus season (8%). Hospitalizations for RSV in older adults typically lasted 3 to 6 days, with substantial proportions requiring intensive care unit admission and mechanical ventilation. Among older adults hospitalized with RSV, the mortality rate was 6% to 8%.

Conclusions

Protection of older adults against RSV could reduce respiratory-related burden, especially as age increases and the prevalence of comorbidities (especially cardiopulmonary comorbidities) grows.

Prospective observational study in two Dutch hospitals to assess the performance of inflammatory plasma markers to determine disease severity of viral respiratory tract infections in children

INTRODUCTION

Respiratory viruses causing lower respiratory tract infections (LRTIs) are a major cause of hospital admissions in children. Since the course of these infections is unpredictable with potential fast deterioration into respiratory failure, infants are easily admitted to the hospital for observation. The aim of this study was to examine whether systemic inflammatory markers can be used to predict severity of disease in children with respiratory viral infections.

METHODS

Blood and nasopharyngeal washings from children <3 years of age with viral LRTI attending a hospital were collected within 24 hours (acute) and after 4-6 weeks (recovery). Patients were assigned to a mild (observation only), moderate (supplemental oxygen and/or nasogastric feeding) or severe (mechanical ventilation) group. Linear regression analysis was used to design a prediction rule using plasma levels of C reactive protein (CRP), serum amyloid A (SAA), pentraxin 3 (PTX3), serum amyloid P component and properdin. This rule was tested in a validation cohort.

RESULTS

One hundred and four children (52% male) were included. A combination of CRP, SAA, PTX3 and properdin was a better indicator of severe disease compared with any of the individual makers and age (69% sensitivity (95% CI 50 to 83), 90% specificity (95% CI 80 to 96)). Validation in 141 patients resulted in 71% sensitivity (95% CI 53 to 85), 87% specificity (95% CI 79 to 92), negative predictive value of 64% (95% CI 47 to 78) and positive predictive value of 90% (95% CI 82 to 95). The prediction rule was not able to identify patients with a mild course of disease.

CONCLUSION

A combination of CRP, SAA, PTX3 and properdin was able to identify children with a severe course of viral LRTI disease, even in children under 2 months of age. To assess the true impact on clinical management, these results should be validated in a prospective randomised control study.

Estimates of hospitalization attributable to influenza and RSV in the US during 1997-2009, by age and risk status

BACKGROUND

Estimates of influenza and respiratory syncytial virus (RSV) burden must be periodically updated to inform public health strategies. We estimated seasonal influenza- and RSV-attributable hospitalizations in the US from 1997 to 2009 according to age and risk status (NCT01599390).

METHODS

Multiple linear regression modelling was used to attribute hospitalizations to influenza or RSV using virological surveillance and hospitalization data. Hospitalization data were obtained from the US Nationwide Inpatient Sample and virology data were obtained from FluView (Centers for Disease Control and Prevention). Outcomes included any mention of ICD-coded respiratory disease and cardiorespiratory disease diagnoses. We also explored a broader definition of respiratory disease that included mention of relevant respiratory sign/symptoms and viral infection ("respiratory broad").

RESULTS

Applying the respiratory broad outcome, our model attributed ~300,000 and ~200,000 hospitalizations to influenza and RSV, respectively. Influenza A/H3N2 was the predominant cause of influenza-related hospitalizations in most seasons, except in three seasons when influenza B was dominant; likewise, A/H3N2 caused most influenza-related hospitalizations in all age segments, except in children <18 years where the relative contribution of A/H3N2 and B was similar. Most influenza A- and B-related hospitalizations occurred in seniors while approximately one half and one third of all RSV-related events occurred in children 0-4 years and seniors 65+ years, respectively. High-risk status was associated with higher risk of both influenza- and RSV-attributable hospitalizations in adults, but not in children.

CONCLUSIONS

Our study assessed the burden of influenza and RSV, information that is important for both cost effectiveness studies and for prioritization of the development of antivirals and vaccines. For seniors, we found that the burdens of influenza and RSV were both substantial. Among children <18 years, about half of all influenza hospitalizations were due to influenza B, most occurring in children without noted risk conditions. RSV hospitalizations among children were confined to those 0-4 years. Our study also demonstrated the importance of the outcome used to estimate hospitalization burden. Our findings highlight the burden of influenza among children regardless of risk status and underscore the prevalence of RSV infections among both young children and older adults.